LVCONVERT(8)

NAME
lvconvert — change LV type and other utilities

SYNOPSIS
lvconvert [OPTION]... VolumeGroup/LogicalVolume OPTIONS:
-b, --background
--cachepolicy Policy
--cachepool CachePoolLogicalVolume{Name|Path}
--cachesettings Key=Value
-c, --chunksize ChunkSize[b|B|s|S|k|K|m|M|g|G]
--corelog
--discards {ignore|nopassdown|passdown}
-i, --interval Seconds
--merge
--mirrorlog {disk|core|mirrored}
-m, --mirrors Number
-n, --name Name
--noudevsync
--originname NewExternalOriginVolumeName
--poolmetadata PoolMetadataLogicalVolume{Name|Path}
--poolmetadatasize PoolMetadataSize[b|B|s|S|k|K|m|M|g|G]
--poolmetadataspare {y|n}
-r, --readahead {ReadAheadSectors|auto|none}
-R, --regionsize MirrorLogRegionSize
--repair
--replace PhysicalVolume
--splitcache
--splitmirrors Number
--splitsnapshot
--stripes Number
-I, --stripesize StripeSize
--type striped
--type snapshot | --snapshot | -s
--type mirror
--type raid*
--type thin | --thin | -T
--type cache | --cache | -H
--type thin-pool
--type cache-pool
--thinpool ThinPoolLogicalVolume{Name|Path}
--trackchanges
--uncache
-Z, --zero {y|n}
Common options:
-A, --alloc AllocationPolicy
-f, --force
--commandprofile ProfileName
-h, -?, --help
-v, --verbose
-y, --yes
--version

DESCRIPTION
lvconvert changes the LV type and includes various LV utilities. To display the current LV type, run the command: lvs -o name,segtype VG/LV To change the LV type, run the command: lvconvert --type NewType VG/LV

  LV types
The LV type is also called the "segment type" or "segtype". LVs with the following types can be modified by lvconvert: striped, snapshot, mirror, raid*, thin, cache, thin-pool, cache-pool. The specific operations available on each LV type are listed below. The linear type is equivalent to the striped type when one 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 mirroring. The raid* type refers to one of many raid levels, e.g. raid1, raid5.

  LV layers
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 sometimes called sub LVs. Changing the LV type will often change the composition of sub LVs. Sub LVs can be displayed with the command lvs -a. A command run on a visible LV sometimes operates on a sub LV rather than the specified LV. These cases are noted below. Sometimes a sub LV must be specified directly on the command line, but this is a non-standard form. These cases may change in the future to avoid the direct use of hidden LVs.

COMMANDS

  Operations on a StripedLV with type striped or linear:
lvconvert --merge VG/StripedLV
• Merge StripedLV into an LV when it is a previously split mirror.
• Options --background, --interval.
• See corresponding operation --splitmirrors. lvconvert --type snapshot VG/StripedLV VG/SnapshotLV
• Recombine StripedLV with SnapshotLV which was previously split.
• Options --chunksize, --zero.
• See corresponding operation --splitsnapshot. lvconvert --type thin VG/StripedLV
• Convert StripedLV to type thin with an external origin.
• StripedLV becomes a read-only external origin LV with a new name.
• Requires --thinpool to specify the thin pool to use.
• Options --originname. lvconvert --type cache VG/StripedLV
• Convert StripedLV to type cache.
• Requires --cachepool to specify the cache pool to use.
• Options --cachepolicy, --cachesettings. lvconvert --type thin-pool VG/StripedLV
• Convert StripedLV to type thin-pool.
• The StripedLV is used for thin pool data.
• Options --chunksize, --discards, --poolmetadata{size,spare},
  --readahead, --zero. lvconvert --type cache-pool VG/StripedLV
• Convert StripedLV to type cache-pool.
• Options --chunksize, --poolmetadata{size,spare}. lvconvert --type mirror VG/StripedLV
• Convert StripedLV to type mirror.
• Requires --mirrors to specify the number of mirrors to use.
• Options --mirrorlog, --regionsize. lvconvert --type raid* VG/StripedLV
• Convert StripedLV to type raid*.
• Required options depend on the raid level.

  Operations on RaidLV with type raid*:
lvconvert --mirrors Number VG/RaidLV
• Change the number of images in raid1 RaidLV. Note the current maximum is 9 providing 10 raid1 legs. lvconvert --splitmirrors Number VG/RaidLV
• Split images from raid1 RaidLV and use them to create a new LV.
• Requires --name for the new LV, or the use of --trackchanges. lvconvert --merge VG/RaidLV
• Merge RaidLV into an LV when it is a previously split mirror.
• Options --background, --interval.
• See corresponding operation --splitmirrors. lvconvert --repair VG/RaidLV
• Replace failed PVs in RaidLV. lvconvert --replace PV VG/RaidLV
• Replace specific PV(s) in a raid* LV with another PV.
• The new PV(s) to use can be optionally specified after the LV.
• Repeat to replace multiple: --replace PV1 --replace PV2 ... lvconvert --type snapshot VG/RaidLV VG/SnapshotLV
• Combine RaidLV with SnapshotLV that was previously split.
• Options --chunksize, --zero.
• See corresponding operation --splitsnapshot. lvconvert --type thin VG/RaidLV
• Convert RaidLV to type thin with an external origin.
• RaidLV becomes a read-only external origin LV with a new name.
• Requires --thinpool to specify the thin pool to use.
• Options --originname. lvconvert --type cache VG/RaidLV
• Convert RaidLV to type cache.
• Requires --cachepool to specify the cache pool to use.
• Options --cachepolicy, --cachesettings. lvconvert --type thin-pool VG/RaidLV
• Convert RaidLV to type thin-pool.
• The RaidLV is used for thin pool data.
• Options --chunksize, --discards, --poolmetadata{size,spare},
  --readahead, --zero. lvconvert --type cache-pool VG/RaidLV
• Convert RaidLV to type cache-pool.
• Options --chunksize, --poolmetadata{size,spare}. lvconvert --type raid* VG/RaidLV
• Convert RaidLV to use a different raid level.
• Required options depend on the raid level. lvconvert --type mirror VG/RaidLV
• Convert RaidLV to type mirror. lvconvert --type striped VG/RaidLV
• Convert RaidLV to type striped. lvconvert --type linear VG/RaidLV
• Convert RaidLV to type linear.

  Operations on MirrorLV with type mirror:
lvconvert --mirrors Number VG/MirrorLV
• Change the number of images in MirrorLV. lvconvert --splitmirrors Number VG/MirrorLV
• Split images from MirrorLV and use them to create a new LV.
• Requires --name for the new LV. lvconvert --mirrorlog LogType VG/MirrorLV
• Change the type of log used by MirrorLV. lvconvert --repair VG/MirrorLV
• Replace failed PVs in MirrorLV. lvconvert --type linear VG/MirrorLV
• Convert MirrorLV to type linear. lvconvert --type raid* VG/MirrorLV
• Convert MirrorLV to type raid*.
• Required options depend on the raid level.

  Operations on CachePoolLV with type cache-pool:
lvconvert --splitcache VG/CachePoolLV
• Split the cache LV from CachePoolLV.
• Equivalent to --splitcache on CacheLV.

  Operations on CacheLV with type cache:
lvconvert --splitcache VG/CacheLV
• Split and keep the cache pool from CacheLV. lvconvert --uncache VG/CacheLV
• Split and remove the cache pool from CacheLV. lvconvert --splitmirrors Number VG/CacheLV
• Split images from the mirrored origin of CacheLV to create a new LV.
• Operates on mirror or raid1 sub LV.
• Requires --name for the new LV, or the use of --trackchanges. lvconvert --type thin-pool VG/CacheLV
• Convert CacheLV to type thin-pool.
• The CacheLV is used for thin pool data.
• Options --chunksize, --discards, --poolmetadata{size,spare},
  --readahead, --zero.

  Operations on ThinPoolLV with type thin-pool:
lvconvert --splitcache VG/ThinPoolLV
• Split and keep the cache pool from the data portion of ThinPoolLV.
• Operates on the data sub LV of the thin pool LV.
• The data sub LV of the thin pool must be a cache LV. lvconvert --uncache VG/ThinPoolLV
• Split and remove the cache pool from the data portion of ThinPoolLV.
• Operates on the data sub LV of the thin pool LV.
• The data sub LV of the thin pool must be a cache LV. lvconvert --type cache VG/ThinPoolLV
• Convert the data portion of ThinPoolLV to type cache.
• Operates on the data sub LV of the thin pool LV.
• Options --cachepolicy, --cachesettings. lvconvert --repair VG/ThinPoolLV
• Repair ThinPoolLV.

  Operations on ThinLV with type thin:
lvconvert --merge VG/ThinLV
• Merge ThinLV into its origin LV.
• ThinLV must have been created as a snapshot of another thin LV.
• Options --background, --interval.

  Operations on SnapshotLV with type snapshot:
lvconvert --splitsnapshot VG/SnapshotLV
• Separate COW snapshot SnapshotLV from its origin LV. lvconvert --merge VG/SnapshotLV
• Merge COW snapshot SnapshotLV into its origin.
• Options --background, --interval.

OPTIONS
See lvm(8) for common options.

-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.

--cachepolicy Policy
Specifies the cache policy for a cache LV. Also see lvmcache(7).

--cachepool CachePoolLogicalVolume{Name|Path}
Specifies the cache pool to use when converting an LV to a cache LV. If CachePoolLogicalVolume is not yet a cache pool, the command will attempt to convert it into a cache pool prior to the cache LV conversion. Also see lvmcache(7).

--cachesettings Key=Value
Specifies tunable values for a cache LV. (The default values should usually be adequate.) The special string value default switches settings back to their default kernel values and removes them from the list of settings stored in LVM metadata. Also see lvmcache(7).

-c, --chunksize ChunkSize[b|B|s|S|k|K|m|M|g|G]
Sets the chunk size for a snapshot, cache pool or thin pool. The default unit is in kilobytes.

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. (Early kernel support until thin target version 1.4 required the value to be a power of 2. Discards were not supported for non-power of 2 values until thin target version 1.5.)

--corelog
Specifies or changes the log type for a mirror LV. It is an alias for --mirrorlog core. (This option does not apply to the raid1 LV type.)

--discards {ignore|nopassdown|passdown}
Specifies if discards will be processed by the thin layer in the kernel and passed down to the Physical Volume. This applies only to thin pools. The default is passdown. Also see lvmthin(7).

-H, --cache
Alias for --type cache. See COMMANDS description for
lvconvert --type cache.

-i, --interval Seconds
Report progress as a percentage at regular intervals.

--merge
Merges a snapshot that was split from an origin LV using --splitsnapshot, back into the origin LV. Merges a raid1 image that was split from a raid1 LV using --splitsnapshot and --trackchanges, back into the original raid1 LV. To check if the kernel supports the snapshot merge feature, look for "snapshot-merge" in the output of dmsetup targets. 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, 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.

--mirrorlog {disk|core|mirrored}
Specifies or changes the log type for a mirror LV. The default is disk, which is persistent and requires a small amount of storage space, usually on a separate device from the data being mirrored. Core may be useful for short-lived mirrors. It means the mirror is regenerated by copying the data from the first device again every time the device is activated - e.g. possibly after every reboot. Using mirrored will create a persistent log that is itself mirrored. (This option does not apply to the raid1 LV type.)

-m, --mirrors Number
Specifies the number mirror images in addition to the original LV image, e.g. --mirrors 1 means two copies of the data, the original and one mirror image. This option is required when converting an LV to a raid1 or mirror LV. This option can be used alone to change the number of mirror images in an existing raid1 or mirror LV. The special case --mirrors 0 has been used historically to indicate a linear LV with no mirror images.

-n, --name Name
Specifies the name to use when the command is creating a new LV, e.g. --splitmirrors.

--noudevsync
Disables udev synchronisation. The process will not wait for notification from udev. It will continue irrespective of any possible udev processing in the background. You should only use this if udev is not running or has rules that ignore the devices LVM creates.

--originname NewExternalOriginVolumeName
Specifies the name to use for the external origin LV when converting an LV to a thin LV. The LV being converted becomes a read-only external origin with this name.
Without this option, the default name of "lvol<n>" will be generated where <n> is the LVM internal number of the LV.

--poolmetadata PoolMetadataLogicalVolume{Name|Path}
Specifies the LV to use for thin pool metadata when converting an LV to a thin pool LV.
Specifies the LV to use for cache pool metadata when converting an LV to a cache pool LV.
The size should be between 2MiB and 16GiB.
(This option can also be used when a thin pool or cache pool are created as an auxiliary operation within a different command.) Also see lvmthin(7), and lvmcache(7).

--poolmetadatasize PoolMetadataSize[b|B|s|S|k|K|m|M|g|G]
Specifies the size of a cache pool metadata LV or a thin pool metadata LV. This is used if a command creates a pool metadata LV automatically as part of the operation. This option is not used when an existing LV is specified as the pool metadata LV, i.e. --poolmetadata. The default unit is megabytes. Also see lvmthin(7), and lvmcache(7).

--poolmetadataspare {y|n}
Specifies if a spare pool metadata LV should be created. A spare pool metadata LV will be used for pool repair. Only one spare pool metadata LV is maintained within a VG, with the size of the largest existing pool metadata LV. The default is yes.

-r, --readahead {ReadAheadSectors|auto|none}
Specifies the read ahead sector count of a thin pool metadata LV. The default value is auto which allows the kernel to choose a suitable value automatically. None is equivalent to specifying zero.

-R, --regionsize MirrorLogRegionSize
A mirror LV is divided into regions of this size (in MB), and the mirror log uses this granularity to track which regions are in sync. (This option does not apply to the raid1 LV type.)

--repair
Replaces failed PVs in a raid1 or mirror LV with other PVs available in the VG. By default, the original number of mirror images will be restored if possible. Specify -y on the command line to skip the prompts. Use -f if you do not want any replacement. You may use --use-policies to use the device replacement policy specified in lvm.conf(5), see activation/mirror_log_fault_policy or activation/mirror_device_fault_policy. When used with a thin pool LV, this option automates the use of the thin_repair(8) tool on the thin pool. This repairs a very limitted number of problems. Only inactive thin pools can be repaired. There is no validation of metadata between kernel and LVM. This requires further manual work. After successfull repair the old unmodified metadata are still available in "<pool>_meta<n>" LV. Also see lvmthin(7).

--replace PhysicalVolume
Remove the specified device PhysicalVolume and replace it with one that is available in the VG, or from a specific list of PVs specified on the command line following the LV name. This option may be repeated multiple times depending on the RaidLV type.

-s, --snapshot
Alias for --type snapshot. See COMMANDS description for
lvconvert --type snapshot.

--split
Separates SplitableLogicalVolume. This option tries to detect the necessary split operation from its arguments. Avoid using this option and use one of the following instead: --splitcache, --splitmirrors, --splitsnapshot.

--splitcache
Separates a cache pool from a cache LV, and keeps the unused cache pool LV. Before the separation, the cache is flushed. See similar option --uncache. Also see lvmcache(7).

--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. lvconvert --merge can be used to recombine the split images with the original raid1 LV. A name can be specified for the new LV with --name (a name is required without --trackchanges).

--splitsnapshot
Separates a COW snapshot from its origin LV. The LV that is split off contains the chunks that differ from the origin LV along with metadata describing them. This LV can be wiped and then destroyed with lvremove. See corresponding operation lvconvert --type snapshot.

--stripes Number
Specifies the number of stripes in a striped LV. This is the number of physical volumes (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 StripeSize
Specifies the stripe size in kilobytes for a striped LV. The stripe size is the number of kilobytes written to each stripe, i.e. to one device, before writing to the next stripe/device. StripeSize must be a power of 2 and cannot exceed the VG physical extent (PE) size.

--type SegmentType
Converts an LV from one segment type to another. See COMMANDS section for a description of converting between each type.

--thinpool ThinPoolLogicalVolume{Name|Path}
Specifies the thin pool to use when converting an LV to a thin LV. If ThinPoolLogicalVolume is not yet a thin pool, the command will attempt to convert it to a thin pool prior to the thin LV conversion. Also see lvmthin(7).

--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 allows the read-only detached image(s) to be merged efficiently back into the raid1 LV later. Only the regions with changed data are resynchronized during merge. (This option only applies to the raid1 LV type.)

-T, --thin
Alias for --type thin. See COMMANDS description for
lvconvert --type thin.

--uncache
Separates a cache pool from a cache LV, and removes the unused cache pool LV. Before the separation, the cache is flushed. See similar option --splitcache. Also see lvmcache(7).

-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 controls zeroing of provisioned blocks. Provisioning of large zeroed chunks negatively impacts performance. Also see lvmthin(7).

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 --splitmirrors and --trackchanges) back into the original raid1 LV:
lvconvert --merge 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:
lvconvert --replace /dev/sdb1 --replace /dev/sdc1 --replace /dev/sdd1
    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 /dev/sd[gh]1 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 128 vg/lvol1 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), lvmcache(7), lvmthin(7), lvdisplay(8), lvextend(8), lvreduce(8), lvremove(8), lvrename(8), lvscan(8), vgcreate(8), cache_dump(8), cache_repair(8), cache_restore(8), thin_dump(8), thin_repair(8), thin_restore(8)