LVCONVERT(8)   (LVM TOOLS 2.03.11(2) (2021-01-08))   LVCONVERT(8)

     NAME
          lvconvert - Change logical volume layout

     SYNOPSIS
          lvconvert option_args position_args
              [ option_args ]
              [ position_args ]

              --alloc
          contiguous|cling|cling_by_tags|normal|anywhere|inherit
           -b|--background
           -H|--cache
              --cachedevice PV
              --cachemetadataformat auto|1|2
              --cachemode writethrough|writeback|passthrough
              --cachepolicy String
              --cachepool LV
              --cachesettings String
              --cachesize Size[m|UNIT]
              --cachevol LV
           -c|--chunksize Size[k|UNIT]
              --commandprofile String
              --compression y|n
              --config String
           -d|--debug
              --deduplication y|n
              --discards passdown|nopassdown|ignore
              --driverloaded y|n
           -f|--force
           -h|--help
           -i|--interval Number
              --lockopt String
              --longhelp
              --merge
              --mergemirrors
              --mergesnapshot
              --mergethin
              --metadataprofile String
              --mirrorlog core|disk
           -m|--mirrors [+|-]Number
           -n|--name String
              --nolocking
              --noudevsync
              --originname LV
              --poolmetadata LV
              --poolmetadatasize Size[m|UNIT]
              --poolmetadataspare y|n
              --profile String
           -q|--quiet
              --raidintegrity y|n

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              --raidintegrityblocksize Number
              --raidintegritymode String
           -r|--readahead auto|none|Number
           -R|--regionsize Size[m|UNIT]
              --repair
              --replace PV
           -s|--snapshot
              --splitcache
              --splitmirrors Number
              --splitsnapshot
              --startpoll
              --stripes Number
           -I|--stripesize Size[k|UNIT]
              --swapmetadata
           -t|--test
           -T|--thin
              --thinpool LV
              --trackchanges
              --type
          linear|striped|snapshot|mirror|raid|thin|cache|vdo|thin-pool|cache-pool|vdo-pool
              --uncache
              --usepolicies
              --vdopool LV
           -v|--verbose
              --version
           -V|--virtualsize Size[m|UNIT]
           -y|--yes
           -Z|--zero y|n

     DESCRIPTION
          lvconvert changes the LV type and includes utilities for  LV
          data  maintenance.  The  LV  type  controls  data layout and
          redundancy.  The LV type is also called the segment type  or
          segtype.

          To display the current LV type, run the command:

          lvs -o name,segtype LV

          In some cases, an LV is a single device  mapper  (dm)  layer
          above  physical  devices.   In  other  cases, hidden LVs (dm
          devices) are layered between the  visible  LV  and  physical
          devices.   LVs  in  the middle layers are called sub LVs.  A
          command run on a visible LV sometimes operates on a  sub  LV
          rather than the specified LV.  In other cases, a sub LV must
          be specified directly on the command line.

          Sub LVs can be displayed with the command:

          lvs -a

          The linear type is equivalent to the striped type  when  one

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          stripe  exists.   In  that  case, the types can sometimes be
          used interchangably.

          In most cases, the mirror type is deprecated and  the  raid1
          type  should be used.  They are both implementations of mir-
          roring.

          Striped raid types are raid0/raid0_meta, raid5 (an alias for
          raid5_ls),  raid6  (an  alias  for  raid6_zr) and raid10 (an
          alias for raid10_near).

          As opposed to mirroring, raid5 and  raid6  stripe  data  and
          calculate  parity  blocks. The parity blocks can be used for
          data block recovery in case devices fail. A  maximum  number
          of  one  device  in  a raid5 LV may fail, and two in case of
          raid6. Striped raid types typically rotate  the  parity  and
          data  blocks  for  performance  reasons,  thus avoiding con-
          tention on a single device. Specific arrangements of  parity
          and  data  blocks (layouts) can be used to optimize I/O per-
          formance, or to convert between raid levels.  See lvmraid(7)
          for more information.

          Layouts of  raid5  rotating  parity  blocks  can  be:  left-
          asymmetric  (raid5_la),  left-symmetric (raid5_ls with alias
          raid5),   right-asymmetric    (raid5_ra),    right-symmetric
          (raid5_rs)  and raid5_n, which doesn't rotate parity blocks.
          Layouts of raid6  are:  zero-restart  (raid6_zr  with  alias
          raid6),    next-restart    (raid6_nr),   and   next-continue
          (raid6_nc).

          Layouts including _n allow for conversion between raid  lev-
          els      (raid5_n     to     raid6     or     raid5_n     to
          striped/raid0/raid0_meta). Additionally, special raid6  lay-
          outs for raid level conversions between raid5 and raid6 are:
          raid6_ls_6, raid6_rs_6,  raid6_la_6  and  raid6_ra_6.  Those
          correspond to their raid5 counterparts (e.g. raid5_rs can be
          directly converted to raid6_rs_6 and vice-versa).

          raid10 (an alias for raid10_near) is  currently  limited  to
          one  data  copy and even number of sub LVs. This is a mirror
          group layout, thus a single sub LV may fail per mirror group
          without data loss.

          Striped raid types  support  converting  the  layout,  their
          stripesize and their number of stripes.

          The striped raid types combined with raid1 allow for conver-
          sion  from  linear-> striped/raid0/raid0_meta and vice-versa
          by e.g. linear <-> raid1 <-> raid5_n (then  adding  stripes)
          <-> striped/raid0/raid0_meta.

     USAGE

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          Convert LV to linear.

          lvconvert --type linear LV
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Convert LV to striped.

          lvconvert --type striped LV
              [ -I|--stripesize Size[k|UNIT] ]
              [ -R|--regionsize Size[m|UNIT] ]
              [ -i|--interval Number ]
              [    --stripes Number ]
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Convert LV to type mirror (also see type raid1),

          lvconvert --type mirror LV
              [ -m|--mirrors [+|-]Number ]
              [ -I|--stripesize Size[k|UNIT] ]
              [ -R|--regionsize Size[m|UNIT] ]
              [ -i|--interval Number ]
              [    --stripes Number ]
              [    --mirrorlog core|disk ]
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Convert LV to raid or change raid layout
          (a specific raid level must be used, e.g. raid1).

          lvconvert --type raid LV
              [ -m|--mirrors [+|-]Number ]
              [ -I|--stripesize Size[k|UNIT] ]
              [ -R|--regionsize Size[m|UNIT] ]
              [ -i|--interval Number ]
              [    --stripes Number ]
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Convert LV to raid1 or mirror, or change  number  of  mirror
          images.

          lvconvert -m|--mirrors [+|-]Number LV
              [ -R|--regionsize Size[m|UNIT] ]
              [ -i|--interval Number ]
              [    --mirrorlog core|disk ]
              [ COMMON_OPTIONS ]

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              [ PV ... ]
          -

          Convert raid LV to change number of stripe images.

          lvconvert --stripes Number LV_raid
              [ -i|--interval Number ]
              [ -R|--regionsize Size[m|UNIT] ]
              [ -I|--stripesize Size[k|UNIT] ]
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Convert raid LV to change the stripe size.

          lvconvert -I|--stripesize Size[k|UNIT] LV_raid
              [ -i|--interval Number ]
              [ -R|--regionsize Size[m|UNIT] ]
              [ COMMON_OPTIONS ]
          -

          Split images from a raid1 or mirror LV and use them to  cre-
          ate a new LV.

          lvconvert    --splitmirrors    Number    -n|--name    LV_new
          LV_cache_mirror_raid1
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Split images from a raid1 LV and track changes to origin for
          later merge.

          lvconvert     --splitmirrors      Number      --trackchanges
          LV_cache_raid1
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Merge LV images that were split from a raid1 LV.

          lvconvert --mergemirrors VG|LV_linear_raid|Tag ...
              [ COMMON_OPTIONS ]
          -

          Convert LV to a thin LV, using the original LV as an  exter-
          nal origin.

          lvconvert       --type       thin       --thinpool        LV
          LV_linear_striped_thin_cache_raid
              [ -T|--thin ]
              [ -r|--readahead auto|none|Number ]

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              [ -c|--chunksize Size[k|UNIT] ]
              [ -Z|--zero y|n ]
              [    --originname LV_new ]
              [    --poolmetadata LV ]
              [    --poolmetadatasize Size[m|UNIT] ]
              [    --poolmetadataspare y|n ]
              [    --metadataprofile String ]
              [ COMMON_OPTIONS ]
          -

          Attach a cache pool to an LV, converts the LV to type cache.

          lvconvert      --type       cache       --cachepool       LV
          LV_linear_striped_thinpool_vdo_vdopool_vdopooldata_raid
              [ -H|--cache ]
              [ -Z|--zero y|n ]
              [ -r|--readahead auto|none|Number ]
              [ -c|--chunksize Size[k|UNIT] ]
              [    --cachemetadataformat auto|1|2 ]
              [    --cachemode writethrough|writeback|passthrough ]
              [    --cachepolicy String ]
              [    --cachesettings String ]
              [    --poolmetadata LV ]
              [    --poolmetadatasize Size[m|UNIT] ]
              [    --poolmetadataspare y|n ]
              [    --metadataprofile String ]
              [ COMMON_OPTIONS ]
          -

          Attach a writecache to an LV, converts the LV to type write-
          cache.

          lvconvert     --type      writecache      --cachevol      LV
          LV_linear_striped_raid
              [    --cachesettings String ]
              [ COMMON_OPTIONS ]
          -

          Attach a cache to an LV, converts the LV to type cache.

          lvconvert       --type       cache       --cachevol       LV
          LV_linear_striped_thinpool_raid
              [ -H|--cache ]
              [ -Z|--zero y|n ]
              [ -c|--chunksize Size[k|UNIT] ]
              [    --cachemetadataformat auto|1|2 ]
              [    --cachemode writethrough|writeback|passthrough ]
              [    --cachepolicy String ]
              [    --cachesettings String ]
              [    --poolmetadatasize Size[m|UNIT] ]
              [ COMMON_OPTIONS ]
          -

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          Add a writecache to an LV, using a specified cache device.

          lvconvert     --type     writecache     --cachedevice     PV
          LV_linear_striped_raid
              [    --cachesize Size[m|UNIT] ]
              [    --cachesettings String ]
              [ COMMON_OPTIONS ]
          -

          Add a cache to an LV, using a specified cache device.

          lvconvert      --type      cache      --cachedevice       PV
          LV_linear_striped_thinpool_raid
              [ -c|--chunksize Size[k|UNIT] ]
              [    --cachesize Size[m|UNIT] ]
              [    --cachesettings String ]
              [ COMMON_OPTIONS ]
          -

          Convert LV to type thin-pool.

          lvconvert --type thin-pool LV_linear_striped_cache_raid
              [ -I|--stripesize Size[k|UNIT] ]
              [ -r|--readahead auto|none|Number ]
              [ -c|--chunksize Size[k|UNIT] ]
              [ -Z|--zero y|n ]
              [    --stripes Number ]
              [    --discards passdown|nopassdown|ignore ]
              [    --poolmetadata LV ]
              [    --poolmetadatasize Size[m|UNIT] ]
              [    --poolmetadataspare y|n ]
              [    --metadataprofile String ]
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Convert LV to type cache-pool.

          lvconvert --type cache-pool LV_linear_striped_raid
              [ -Z|--zero y|n ]
              [ -r|--readahead auto|none|Number ]
              [ -c|--chunksize Size[k|UNIT] ]
              [    --cachemetadataformat auto|1|2 ]
              [    --cachemode writethrough|writeback|passthrough ]
              [    --cachepolicy String ]
              [    --cachesettings String ]
              [    --poolmetadata LV ]
              [    --poolmetadatasize Size[m|UNIT] ]
              [    --poolmetadataspare y|n ]
              [    --metadataprofile String ]
              [ COMMON_OPTIONS ]
              [ PV ... ]

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          -

          Convert LV to type vdopool.

          lvconvert --type vdo-pool LV_linear_striped_cache_raid
              [ -n|--name LV_new ]
              [ -V|--virtualsize Size[m|UNIT] ]
              [    --compression y|n ]
              [    --deduplication y|n ]
              [ COMMON_OPTIONS ]
          -

          Detach a cache from an LV.

          lvconvert                                       --splitcache
          LV_thinpool_cache_cachepool_vdopool_writecache
              [    --cachesettings String ]
              [ COMMON_OPTIONS ]
          -

          Merge thin LV into its origin LV.

          lvconvert --mergethin LV_thin ...
              [ COMMON_OPTIONS ]
          -

          Merge COW snapshot LV into its origin.

          lvconvert --mergesnapshot LV_snapshot ...
              [ -i|--interval Number ]
              [ COMMON_OPTIONS ]
          -

          Combine a former COW snapshot (second arg) with a former
          origin LV (first arg) to reverse a splitsnapshot command.

          lvconvert --type snapshot LV LV_linear_striped
              [ -s|--snapshot ]
              [ -c|--chunksize Size[k|UNIT] ]
              [ -Z|--zero y|n ]
              [ COMMON_OPTIONS ]
          -

          Replace failed PVs in a raid or mirror LV.
          Repair a thin pool.
          Repair a cache pool.

          lvconvert --repair LV_thinpool_cache_cachepool_mirror_raid
              [ -i|--interval Number ]
              [    --usepolicies ]
              [    --poolmetadataspare y|n ]
              [ COMMON_OPTIONS ]

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              [ PV ... ]
          -

          Replace specific PV(s) in a raid LV with another PV.

          lvconvert --replace PV LV_raid
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Poll LV to continue conversion.

          lvconvert --startpoll LV_mirror_raid
              [ COMMON_OPTIONS ]
          -

          Add or remove data integrity checksums to raid images.

          lvconvert --raidintegrity y|n LV_raid
              [    --raidintegritymode String ]
              [    --raidintegrityblocksize Number ]
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Common options for command:
              [ -b|--background ]
              [ -f|--force ]
              [    --alloc
              contiguous|cling|cling_by_tags|normal|anywhere|inherit ]
              [    --noudevsync ]

          Common options for lvm:
              [ -d|--debug ]
              [ -h|--help ]
              [ -q|--quiet ]
              [ -t|--test ]
              [ -v|--verbose ]
              [ -y|--yes ]
              [    --commandprofile String ]
              [    --config String ]
              [    --driverloaded y|n ]
              [    --lockopt String ]
              [    --longhelp ]
              [    --nolocking ]
              [    --profile String ]
              [    --version ]

     OPTIONS
          --alloc
               contiguous|cling|cling_by_tags|normal|anywhere|inherit
               Determines the allocation policy when a command needs

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               to allocate Physical Extents (PEs) from the VG. Each VG
               and LV has an allocation policy which can be changed
               with vgchange/lvchange, or overriden on the command
               line.  normal applies common sense rules such as not
               placing parallel stripes on the same PV.  inherit
               applies the VG policy to an LV.  contiguous requires
               new PEs be placed adjacent to existing PEs.  cling
               places new PEs on the same PV as existing PEs in the
               same stripe of the LV.  If there are sufficient PEs for
               an allocation, but normal does not use them, anywhere
               will use them even if it reduces performance, e.g. by
               placing two stripes on the same PV.  Optional posi-
               tional PV args on the command line can also be used to
               limit which PVs the command will use for allocation.
               See lvm(8) for more information about allocation.

          -b|--background
               If the operation requires polling, this option causes
               the command to return before the operation is complete,
               and polling is done in the background.

          -H|--cache
               Specifies the command is handling a cache LV or cache
               pool.  See --type cache and --type cache-pool.  See
               lvmcache(7) for more information about LVM caching.

          --cachedevice PV
               The name of a device to use for a cache.

          --cachemetadataformat auto|1|2
               Specifies the cache metadata format used by cache tar-
               get.

          --cachemode writethrough|writeback|passthrough
               Specifies when writes to a cache LV should be consid-
               ered complete.  writeback considers a write complete as
               soon as it is stored in the cache pool.  writethough
               considers a write complete only when it has been stored
               in both the cache pool and on the origin LV.  While
               writethrough may be slower for writes, it is more
               resilient if something should happen to a device asso-
               ciated with the cache pool LV. With passthrough, all
               reads are served from the origin LV (all reads miss the
               cache) and all writes are forwarded to the origin LV;
               additionally, write hits cause cache block invalidates.
               See lvmcache(7) for more information.

          --cachepolicy String
               Specifies the cache policy for a cache LV.  See lvm-
               cache(7) for more information.

          --cachepool LV

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               The name of a cache pool.

          --cachesettings String
               Specifies tunable values for a cache LV in "Key =
               Value" form.  Repeat this option to specify multiple
               values.  (The default values should usually be ade-
               quate.)  The special string value default switches set-
               tings back to their default kernel values and removes
               them from the list of settings stored in LVM metadata.
               See lvmcache(7) for more information.

          --cachesize Size[m|UNIT]
               The size of cache to use.

          --cachevol LV
               The name of a cache volume.

          -c|--chunksize Size[k|UNIT]
               The size of chunks in a snapshot, cache pool or thin
               pool.  For snapshots, the value must be a power of 2
               between 4KiB and 512KiB and the default value is 4.
               For a cache pool the value must be between 32KiB and
               1GiB and the default value is 64.  For a thin pool the
               value must be between 64KiB and 1GiB and the default
               value starts with 64 and scales up to fit the pool
               metadata size within 128MiB, if the pool metadata size
               is not specified.  The value must be a multiple of
               64KiB.  See lvmthin(7) and lvmcache(7) for more infor-
               mation.

          --commandprofile String
               The command profile to use for command configuration.
               See lvm.conf(5) for more information about profiles.

          --compression y|n
               Controls whether compression is enabled or disable for
               VDO volume.  See lvmvdo(7) for more information about
               VDO usage.

          --config String
               Config settings for the command. These override
               lvm.conf settings.  The String arg uses the same format
               as lvm.conf, or may use section/field syntax.  See
               lvm.conf(5) for more information about config.

          -d|--debug ...
               Set debug level. Repeat from 1 to 6 times to increase
               the detail of messages sent to the log file and/or sys-
               log (if configured).

          --deduplication y|n
               Controls whether deduplication is enabled or disable

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               for VDO volume.  See lvmvdo(7) for more information
               about VDO usage.

          --discards passdown|nopassdown|ignore
               Specifies how the device-mapper thin pool layer in the
               kernel should handle discards.  ignore causes the thin
               pool to ignore discards.  nopassdown causes the thin
               pool to process discards itself to allow reuse of
               unneeded extents in the thin pool.  passdown causes the
               thin pool to process discards itself (like nopassdown)
               and pass the discards to the underlying device.  See
               lvmthin(7) for more information.

          --driverloaded y|n
               If set to no, the command will not attempt to use
               device-mapper.  For testing and debugging.

          -f|--force ...
               Override various checks, confirmations and protections.
               Use with extreme caution.

          -h|--help
               Display help text.

          -i|--interval Number
               Report progress at regular intervals.

          --lockopt String
               Used to pass options for special cases to lvmlockd.
               See lvmlockd(8) for more information.

          --longhelp
               Display long help text.

          --merge
               An alias for --mergethin, --mergemirrors, or --merges-
               napshot, depending on the type of LV.

          --mergemirrors
               Merge LV images that were split from a raid1 LV.  See
               --splitmirrors with --trackchanges.

          --mergesnapshot
               Merge COW snapshot LV into its origin.  When merging a
               snapshot, if both the origin and snapshot LVs are not
               open, the merge will start immediately. Otherwise, the
               merge will start the first time either the origin or
               snapshot LV are activated and both are closed. Merging
               a snapshot into an origin that cannot be closed, for
               example a root filesystem, is deferred until the next
               time the origin volume is activated. When merging
               starts, the resulting LV will have the origin's name,

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               minor number and UUID. While the merge is in progress,
               reads or writes to the origin appear as being directed
               to the snapshot being merged. When the merge finishes,
               the merged snapshot is removed.  Multiple snapshots may
               be specified on the command line or a @tag may be used
               to specify multiple snapshots be merged to their
               respective origin.

          --mergethin
               Merge thin LV into its origin LV.  The origin thin LV
               takes the content of the thin snapshot, and the thin
               snapshot LV is removed.  See lvmthin(7) for more infor-
               mation.

          --metadataprofile String
               The metadata profile to use for command configuration.
               See lvm.conf(5) for more information about profiles.

          --mirrorlog core|disk
               Specifies the type of mirror log for LVs with the "mir-
               ror" type (does not apply to the "raid1" type.)  disk
               is a persistent log and requires a small amount of
               storage space, usually on a separate device from the
               data being mirrored.  core is not persistent; the log
               is kept only in memory.  In this case, the mirror must
               be synchronized (by copying LV data from the first
               device to others) each time the LV is activated, e.g.
               after reboot.  mirrored is a persistent log that is
               itself mirrored, but should be avoided. Instead, use
               the raid1 type for log redundancy.

          -m|--mirrors [+|-]Number
               Specifies the number of mirror images in addition to
               the original LV image, e.g. --mirrors 1 means there are
               two images of the data, the original and one mirror
               image.  Optional positional PV args on the command line
               can specify the devices the images should be placed on.
               There are two mirroring implementations: "raid1" and
               "mirror".  These are the names of the corresponding LV
               types, or "segment types".  Use the --type option to
               specify which to use (raid1 is default, and mirror is
               legacy) Use lvm.conf global/mirror_segtype_default and
               global/raid10_segtype_default to configure the default
               types.  The plus prefix + can be used, in which case
               the number is added to the current number of images, or
               the minus prefix - can be used, in which case the num-
               ber is subtracted from the current number of images.
               See lvmraid(7) for more information.

          -n|--name String
               Specifies the name of a new LV.  When unspecified, a
               default name of "lvol#" is generated, where # is a

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               number generated by LVM.

          --nolocking
               Disable locking.

          --noudevsync
               Disables udev synchronisation. The process will not
               wait for notification from udev. It will continue irre-
               spective of any possible udev processing in the back-
               ground. Only use this if udev is not running or has
               rules that ignore the devices LVM creates.

          --originname LV
               Specifies the name to use for the external origin LV
               when converting an LV to a thin LV. The LV being con-
               verted becomes a read-only external origin with this
               name.

          --poolmetadata LV
               The name of a an LV to use for storing pool metadata.

          --poolmetadatasize Size[m|UNIT]
               Specifies the size of the new pool metadata LV.

          --poolmetadataspare y|n
               Enable or disable the automatic creation and management
               of a spare pool metadata LV in the VG. A spare metadata
               LV is reserved space that can be used when repairing a
               pool.

          --profile String
               An alias for --commandprofile or --metadataprofile,
               depending on the command.

          -q|--quiet ...
               Suppress output and log messages. Overrides --debug and
               --verbose.  Repeat once to also suppress any prompts
               with answer 'no'.

          --raidintegrity y|n
               Enable or disable data integrity checksums for raid
               images.

          --raidintegrityblocksize Number
               The block size to use for dm-integrity on raid images.
               The integrity block size should usually match the
               device logical block size, or the file system block
               size.  It may be less than the file system block size,
               but not less than the device logical block size.  Pos-
               sible values: 512, 1024, 2048, 4096.

          --raidintegritymode String

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               Use a journal (default) or bitmap for keeping integrity
               checksums consistent in case of a crash. The bitmap
               areas are recalculated after a crash, so corruption in
               those areas would not be detected. A journal does not
               have this problem.  The journal mode doubles writes to
               storage, but can improve performance for scattered
               writes packed into a single journal write.  bitmap mode
               can in theory achieve full write throughput of the
               device, but would not benefit from the potential scat-
               tered write optimization.

          -r|--readahead auto|none|Number
               Sets read ahead sector count of an LV.  auto is the
               default which allows the kernel to choose a suitable
               value automatically.  none is equivalent to zero.

          -R|--regionsize Size[m|UNIT]
               Size of each raid or mirror synchronization region.
               lvm.conf activation/raid_region_size can be used to
               configure a default.

          --repair
               Replace failed PVs in a raid or mirror LV, or run a
               repair utility on a thin pool. See lvmraid(7) and
               lvmthin(7) for more information.

          --replace PV
               Replace a specific PV in a raid LV with another PV.
               The new PV to use can be optionally specified after the
               LV.  Multiple PVs can be replaced by repeating this
               option.  See lvmraid(7) for more information.

          -s|--snapshot
               Combine a former COW snapshot LV with a former origin
               LV to reverse a previous --splitsnapshot command.

          --splitcache
               Separates a cache pool from a cache LV, and keeps the
               unused cache pool LV.  Before the separation, the cache
               is flushed. Also see --uncache.

          --splitmirrors Number
               Splits the specified number of images from a raid1 or
               mirror LV and uses them to create a new LV. If
               --trackchanges is also specified, changes to the raid1
               LV are tracked while the split LV remains detached.  If
               --name is specified, then the images are permanently
               split from the original LV and changes are not tracked.

          --splitsnapshot
               Separates a COW snapshot from its origin LV. The LV
               that is split off contains the chunks that differ from

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               the origin LV along with metadata describing them. This
               LV can be wiped and then destroyed with lvremove.

          --startpoll
               Start polling an LV to continue processing a conver-
               sion.

          --stripes Number
               Specifies the number of stripes in a striped LV. This
               is the number of PVs (devices) that a striped LV is
               spread across. Data that appears sequential in the LV
               is spread across multiple devices in units of the
               stripe size (see --stripesize). This does not apply to
               existing allocated space, only newly allocated space
               can be striped.

          -I|--stripesize Size[k|UNIT]
               The amount of data that is written to one device before
               moving to the next in a striped LV.

          --swapmetadata
               Extracts the metadata LV from a pool and replaces it
               with another specified LV.  The extracted LV is pre-
               served and given the name of the LV that replaced it.
               Use for repair only. When the metadata LV is swapped
               out of the pool, it can be activated directly and used
               with thin provisioning tools: cache_dump(8),
               cache_repair(8), cache_restore(8), thin_dump(8),
               thin_repair(8), thin_restore(8).

          -t|--test
               Run in test mode. Commands will not update metadata.
               This is implemented by disabling all metadata writing
               but nevertheless returning success to the calling func-
               tion. This may lead to unusual error messages in
               multi-stage operations if a tool relies on reading back
               metadata it believes has changed but hasn't.

          -T|--thin
               Specifies the command is handling a thin LV or thin
               pool.  See --type thin, --type thin-pool, and --virtu-
               alsize.  See lvmthin(7) for more information about LVM
               thin provisioning.

          --thinpool LV
               The name of a thin pool LV.

          --trackchanges
               Can be used with --splitmirrors on a raid1 LV. This
               causes changes to the original raid1 LV to be tracked
               while the split images remain detached. This is a tem-
               porary state that allows the read-only detached image

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               to be merged efficiently back into the raid1 LV later.
               Only the regions with changed data are resynchronized
               during merge.  While a raid1 LV is tracking changes,
               operations on it are limited to merging the split image
               (see --mergemirrors) or permanently splitting the image
               (see --splitmirrors with --name.

          --type
               linear|striped|snapshot|mirror|raid|thin|cache|vdo|thin-pool|cache-pool|vdo-pool
               The LV type, also known as "segment type" or "segtype".
               See usage descriptions for the specific ways to use
               these types.  For more information about redundancy and
               performance (raid<N>, mirror, striped, linear) see lvm-
               raid(7).  For thin provisioning (thin, thin-pool) see
               lvmthin(7).  For performance caching (cache,
               cache-pool) see lvmcache(7).  For copy-on-write snap-
               shots (snapshot) see usage definitions.  For VDO (vdo)
               see lvmvdo(7).  Several commands omit an explicit type
               option because the type is inferred from other options
               or shortcuts (e.g. --stripes, --mirrors, --snapshot,
               --virtualsize, --thin, --cache, --vdo).  Use inferred
               types with care because it can lead to unexpected
               results.

          --uncache
               Separates a cache pool from a cache LV, and deletes the
               unused cache pool LV.  Before the separation, the cache
               is flushed. Also see --splitcache.

          --usepolicies
               Perform an operation according to the policy configured
               in lvm.conf or a profile.

          --vdopool LV
               The name of a VDO pool LV.  See lvmvdo(7) for more
               information about VDO usage.

          -v|--verbose ...
               Set verbose level. Repeat from 1 to 4 times to increase
               the detail of messages sent to stdout and stderr.

          --version
               Display version information.

          -V|--virtualsize Size[m|UNIT]
               The virtual size of a new thin LV.  See lvmthin(7) for
               more information about LVM thin provisioning.  Using
               virtual size (-V) and actual size (-L) together creates
               a sparse LV.  lvm.conf global/sparse_segtype_default
               determines the default segment type used to create a
               sparse LV.  Anything written to a sparse LV will be
               returned when reading from it.  Reading from other

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               areas of the LV will return blocks of zeros.  When
               using a snapshot to create a sparse LV, a hidden vir-
               tual device is created using the zero target, and the
               LV has the suffix _vorigin.  Snapshots are less effi-
               cient than thin provisioning when creating large sparse
               LVs (GiB).

          -y|--yes
               Do not prompt for confirmation interactively but always
               assume the answer yes. Use with extreme caution.  (For
               automatic no, see -qq.)

          -Z|--zero y|n
               For snapshots, this controls zeroing of the first 4KiB
               of data in the snapshot. If the LV is read-only, the
               snapshot will not be zeroed.  For thin pools, this con-
               trols zeroing of provisioned blocks.  Provisioning of
               large zeroed chunks negatively impacts performance.

     VARIABLES
          VG
               Volume Group name.  See lvm(8) for valid names.

          LV
               Logical Volume name.  See lvm(8) for valid  names.   An
               LV positional arg generally includes the VG name and LV
               name, e.g. VG/LV.  LV  followed  by  _<type>  indicates
               that  an LV of the given type is required. (raid repre-
               sents raid<N> type)

          PV
               Physical Volume name, a device path  under  /dev.   For
               commands managing physical extents, a PV positional arg
               generally accepts a suffix indicating a range (or  mul-
               tiple ranges) of physical extents (PEs). When the first
               PE is omitted, it defaults to the start of the  device,
               and  when  the  last  PE is omitted it defaults to end.
               Start and end range (inclusive):  PV[:PE-PE]...   Start
               and length range (counting from 0): PV[:PE+PE]...

          Tag
               Tag name.  See lvm(8) for information about  tag  names
               and using tags in place of a VG, LV or PV.

          String
               See the option description for  information  about  the
               string content.

          Size[UNIT]
               Size is an input number that accepts an optional  unit.
               Input  units  are  always  treated  as base two values,
               regardless of capitalization, e.g.  'k'  and  'K'  both

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               refer  to 1024.  The default input unit is specified by
               letter, followed by |UNIT.  UNIT represents other  pos-
               sible input units: bBsSkKmMgGtTpPeE.  b|B is bytes, s|S
               is sectors of 512 bytes, k|K is KiB, m|M is MiB, g|G is
               GiB,  t|T is TiB, p|P is PiB, e|E is EiB.  (This should
               not be confused with the output control --units,  where
               capital letters mean multiple of 1000.)

     ENVIRONMENT VARIABLES
          See lvm(8) for information about environment variables  used
          by  lvm.   For example, LVM_VG_NAME can generally be substi-
          tuted for a required VG parameter.

     ADVANCED USAGE
          Alternate command forms, advanced command usage, and listing
          of all valid syntax for completeness.

          Change the region size of an LV.

          lvconvert -R|--regionsize Size[m|UNIT] LV_raid
              [ COMMON_OPTIONS ]
          -

          Change the type of mirror log used by a mirror LV.

          lvconvert --mirrorlog core|disk LV_mirror
              [ COMMON_OPTIONS ]
              [ PV ... ]
          -

          Convert LV to a thin LV, using the original LV as an  exter-
          nal origin
          (infers --type thin).

          lvconvert          -T|--thin          --thinpool          LV
          LV_linear_striped_thin_cache_raid
              [ -r|--readahead auto|none|Number ]
              [ -c|--chunksize Size[k|UNIT] ]
              [ -Z|--zero y|n ]
              [    --type thin ]
              [    --originname LV_new ]
              [    --poolmetadata LV ]
              [    --poolmetadatasize Size[m|UNIT] ]
              [    --poolmetadataspare y|n ]
              [    --metadataprofile String ]
              [ COMMON_OPTIONS ]
          -

          Attach a cache pool to an LV (infers --type cache).

          lvconvert         -H|--cache         --cachepool          LV
          LV_linear_striped_thinpool_vdo_vdopool_vdopooldata_raid

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              [ -Z|--zero y|n ]
              [ -r|--readahead auto|none|Number ]
              [ -c|--chunksize Size[k|UNIT] ]
              [    --type cache ]
              [    --cachemetadataformat auto|1|2 ]
              [    --cachemode writethrough|writeback|passthrough ]
              [    --cachepolicy String ]
              [    --cachesettings String ]
              [    --poolmetadata LV ]
              [    --poolmetadatasize Size[m|UNIT] ]
              [    --poolmetadataspare y|n ]
              [    --metadataprofile String ]
              [ COMMON_OPTIONS ]
          -

          Attach a cache to an LV, converts the LV to type cache.

          lvconvert         -H|--cache          --cachevol          LV
          LV_linear_striped_thinpool_raid
              [ -Z|--zero y|n ]
              [ -c|--chunksize Size[k|UNIT] ]
              [    --cachemetadataformat auto|1|2 ]
              [    --cachemode writethrough|writeback|passthrough ]
              [    --cachepolicy String ]
              [    --cachesettings String ]
              [    --poolmetadatasize Size[m|UNIT] ]
              [ COMMON_OPTIONS ]
          -

          Convert LV to type vdopool.

          lvconvert --vdopool LV_linear_striped_cache_raid
              [ -n|--name LV_new ]
              [ -V|--virtualsize Size[m|UNIT] ]
              [    --type vdo-pool ]
              [    --compression y|n ]
              [    --deduplication y|n ]
              [ COMMON_OPTIONS ]
          -

          Detach and delete a cache from an LV.

          lvconvert --uncache LV_thinpool_cache_vdopool_writecache
              [    --cachesettings String ]
              [ COMMON_OPTIONS ]
          -

          Swap metadata LV in a thin pool or cache  pool  (for  repair
          only).

          lvconvert       --swapmetadata       --poolmetadata       LV
          LV_thinpool_cachepool

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              [ -c|--chunksize Size[k|UNIT] ]
              [ COMMON_OPTIONS ]
          -

          Merge  LV  that  was  split  from  a  mirror  (variant,  use
          --mergemirrors).
          Merge thin LV into its origin LV (variant, use --mergethin).
          Merge  COW  snapshot  LV  into  its  origin  (variant,   use
          --mergesnapshot).

          lvconvert                                            --merge
          VG|LV_linear_striped_snapshot_thin_raid|Tag ...
              [ -i|--interval Number ]
              [ COMMON_OPTIONS ]
          -

          Separate a COW snapshot from its origin LV.

          lvconvert --splitsnapshot LV_snapshot
              [ COMMON_OPTIONS ]
          -

          Combine a former COW snapshot (second arg) with a former
          origin LV (first arg) to reverse a splitsnapshot command.

          lvconvert -s|--snapshot LV LV_linear_striped
              [ -c|--chunksize Size[k|UNIT] ]
              [ -Z|--zero y|n ]
              [    --type snapshot ]
              [ COMMON_OPTIONS ]
          -

          Poll LV to continue conversion (also see --startpoll)
          or waits till conversion/mirror syncing is finished

          lvconvert LV_mirror_raid
              [ COMMON_OPTIONS ]
          -

     NOTES
          This previous command syntax  would  perform  two  different
          operations:
          lvconvert --thinpool LV1 --poolmetadata LV2
          If LV1 was not a thin pool, the command would convert LV1 to
          a  thin  pool, optionally using a specified LV for metadata.
          But, if LV1 was already a thin pool, the command would  swap
          the current metadata LV with LV2 (for repair purposes.)

          In the same way, this previous command syntax would  perform
          two different operations:
          lvconvert --cachepool LV1 --poolmetadata LV2

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          If LV1 was not a cache pool, the command would  convert  LV1
          to  a  cache pool, optionally using a specified LV for meta-
          data.  But, if LV1 was already a  cache  pool,  the  command
          would swap the current metadata LV with LV2 (for repair pur-
          poses.)

     EXAMPLES
          Convert a linear LV to a two-way mirror LV.
          lvconvert --type mirror --mirrors 1 vg/lvol1

          Convert a linear LV to a two-way RAID1 LV.
          lvconvert --type raid1 --mirrors 1 vg/lvol1

          Convert a mirror LV to use an in-memory log.
          lvconvert --mirrorlog core vg/lvol1

          Convert a mirror LV to use a disk log.
          lvconvert --mirrorlog disk vg/lvol1

          Convert a mirror or raid1 LV to a linear LV.
          lvconvert --type linear vg/lvol1

          Convert a mirror LV to a raid1 LV with the  same  number  of
          images.
          lvconvert --type raid1 vg/lvol1

          Convert a linear LV to a two-way mirror LV,  allocating  new
          extents from specific PV ranges.
          lvconvert --mirrors 1 vg/lvol1 /dev/sda:0-15 /dev/sdb:0-15

          Convert a mirror LV to a linear LV, freeing physical extents
          from a specific PV.
          lvconvert --type linear vg/lvol1 /dev/sda

          Split one image from a mirror or raid1 LV, making it  a  new
          LV.
          lvconvert --splitmirrors 1 --name lv_split vg/lvol1

          Split one image from a raid1 LV, and track changes  made  to
          the raid1 LV while the split image remains detached.
          lvconvert --splitmirrors 1 --trackchanges vg/lvol1

          Merge an image (that was previously created with --splitmir-
          rors and --trackchanges) back into the original raid1 LV.
          lvconvert --mergemirrors vg/lvol1_rimage_1

          Replace PV /dev/sdb1 with PV /dev/sdf1 in  a  raid1/4/5/6/10
          LV.
          lvconvert --replace /dev/sdb1 vg/lvol1 /dev/sdf1

          Replace 3 PVs /dev/sd[b-d]1  with  PVs  /dev/sd[f-h]1  in  a
          raid1 LV.

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          lvconvert --replace /dev/sdb1 --replace /dev/sdc1 --replace
               vg/lvol1 /dev/sd[fgh]1

          Replace  the  maximum  of  2  PVs  /dev/sd[bc]1   with   PVs
          /dev/sd[gh]1 in a raid6 LV.
          lvconvert --replace /dev/sdb1 --replace /dev/sdc1 vg/lvol1

          Convert an LV into a thin LV in  the  specified  thin  pool.
          The  existing LV is used as an external read-only origin for
          the new thin LV.
          lvconvert --type thin --thinpool vg/tpool1 vg/lvol1

          Convert an LV into a thin LV in  the  specified  thin  pool.
          The  existing LV is used as an external read-only origin for
          the new thin LV, and is renamed "external".
          lvconvert --type thin --thinpool vg/tpool1
               --originname external vg/lvol1

          Convert an LV to a cache pool LV using another specified  LV
          for cache pool metadata.
          lvconvert  --type  cache-pool  --poolmetadata   vg/poolmeta1
          vg/lvol1

          Convert an LV to a cache LV using the specified  cache  pool
          and chunk size.
          lvconvert --type cache --cachepool vg/cpool1 -c

          Detach and keep the cache pool from a cache LV.
          lvconvert --splitcache vg/lvol1

          Detach and remove the cache pool from a cache LV.
          lvconvert --uncache vg/lvol1

     SEE ALSO
          lvm(8) lvm.conf(5) lvmconfig(8)

          pvchange(8)  pvck(8)  pvcreate(8)   pvdisplay(8)   pvmove(8)
          pvremove(8) pvresize(8) pvs(8) pvscan(8)

          vgcfgbackup(8)    vgcfgrestore(8)    vgchange(8)     vgck(8)
          vgcreate(8)     vgconvert(8)     vgdisplay(8)    vgexport(8)
          vgextend(8)    vgimport(8)    vgimportclone(8)    vgmerge(8)
          vgmknodes(8)   vgreduce(8)  vgremove(8)  vgrename(8)  vgs(8)
          vgscan(8) vgsplit(8)

          lvcreate(8)    lvchange(8)     lvconvert(8)     lvdisplay(8)
          lvextend(8)  lvreduce(8) lvremove(8) lvrename(8) lvresize(8)
          lvs(8) lvscan(8)

          lvm-fullreport(8) lvm-lvpoll(8) lvm2-activation-generator(8)
          blkdeactivate(8) lvmdump(8)

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          dmeventd(8)    lvmpolld(8)     lvmlockd(8)     lvmlockctl(8)
          cmirrord(8) lvmdbusd(8)

          lvmsystemid(7)    lvmreport(7)     lvmraid(7)     lvmthin(7)
          lvmcache(7)

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