LVCONVERT(8)

NAME
lvconvert — Change logical volume layout

SYNOPSIS

lvconvert option_args position_args
    [ option_args ]
    [ position_args ]

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

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

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 contention on a single device. Specific arrangements of parity and data blocks (layouts) can be used to optimize I/O performance, 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 levels (raid5_n to raid6 or raid5_n to striped/raid0/raid0_meta). Additionally, special raid6 layouts 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 conversion from linear → striped/raid0/raid0_meta and vice-versa by e.g. linear ↔ raid1 ↔ raid5_n (then adding stripes) ↔ striped/raid0/raid0_meta.

USAGE
Convert LV to linear.

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

—

Convert LV to striped.

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

—

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

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

—

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

lvconvert LV
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    [ COMMON_OPTIONS ]
    [ PV ... ]

—

Convert raid LV to change number of stripe images.

lvconvert LV1
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: raid

—

Convert raid LV to change the stripe size.

lvconvert LV1
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    [ COMMON_OPTIONS ]

    LV1 types: raid

—

Split images from a raid1 or mirror LV and use them to create a new LV.

lvconvert -n|--name LV_new LV1
    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: cache mirror raid1

—

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

lvconvert LV1
    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: cache raid1

—

Merge LV images that were split from a raid1 LV.

lvconvert VG|LV1|Tag ...
    [ COMMON_OPTIONS ]

    LV1 types: linear raid

—

Convert LV to a thin LV, using the original LV as an external origin.

lvconvert --thinpool LV --type thin LV1
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: linear striped cache raid thin zero error

—

Convert LV to a thin LV, using LV as thin-pool data volume.

lvconvert --type thin LV1
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: linear striped cache raid vdo writecache zero error

—

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

lvconvert --cachepool LV --type cache LV1
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: linear striped raid thin thinpool thinpooldata vdo vdopool vdopooldata zero error

—

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

lvconvert --type writecache LV1
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    [ COMMON_OPTIONS ]

    LV1 types: linear striped raid thinpool

—

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

lvconvert --type cache LV1
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    [ COMMON_OPTIONS ]

    LV1 types: linear striped raid thinpool

—

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

lvconvert --type writecache LV1
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    [ COMMON_OPTIONS ]

    LV1 types: linear striped raid thinpool

—

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

lvconvert --type cache LV1
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    [ COMMON_OPTIONS ]

    LV1 types: linear striped raid thinpool

—

Convert LV to type thin-pool (existing data on LV will be erased).

lvconvert --type thin-pool LV1
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: linear striped cache raid vdo writecache zero error

—

Convert LV to type cache-pool (existing data on LV will be erased).

lvconvert --type cache-pool LV1
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: linear striped raid zero error

—

Convert LV to type vdopool (existing data on LV will be erased).

lvconvert --type vdo-pool LV1
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    [ COMMON_OPTIONS ]

    LV1 types: linear striped cache raid

—

Detach a cache from an LV.

lvconvert LV1
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    [ COMMON_OPTIONS ]

    LV1 types: cache cachepool thinpool vdopool writecache

—

Merge thin LV into its origin LV.

lvconvert LV1 ...
    [ COMMON_OPTIONS ]

    LV1 types: thin

—

Merge COW snapshot LV into its origin.

lvconvert LV1 ...
    [ ]
    [ COMMON_OPTIONS ]

    LV1 types: snapshot

—

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

lvconvert --type snapshot LV LV1
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    [ COMMON_OPTIONS ]

    LV1 types: linear striped

—

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

lvconvert LV1
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: cache cachepool mirror raid thinpool

—

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

lvconvert LV1
    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: raid

—

Poll LV to continue conversion.

lvconvert LV1
    [ COMMON_OPTIONS ]

    LV1 types: mirror raid

—

Add or remove data integrity checksums to raid images.

lvconvert LV1
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: raid

—

Common options for command:
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Common options for lvm:
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OPTIONS

Determines the allocation policy when a command needs to allocate
    Physical Extents (PEs) from the VG. Each VG and LV has an allocation policy which can be changed with vgchange/lvchange, or overridden 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 to 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 positional 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.

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

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.

The name of a device to use for a cache.

Specifies the cache metadata format used by cache target.

Specifies when writes to a cache LV should be considered complete.
    writeback considers a write complete as soon as it is stored in the cache pool. writethrough 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 associated 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.

Specifies the cache policy for a cache LV.
    See lvmcache(7) for more information.

The name of a cache pool.

Specifies tunable kernel options for dm-cache or dm-writecache LVs.
    Use the form 'option=value' or 'option1=value option2=value', or repeat --cachesettings for each option being set. These settings override the default kernel behaviors which are usually adequate. To remove cachesettings and revert to the default kernel behaviors, use --cachesettings 'default' for dm-cache or an empty string --cachesettings '' for dm-writecache. See lvmcache(7) for more information.

The size of cache to use.

The name of a cache volume.

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

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

Controls whether compression is enabled or disabled for VDO volume.
    See lvmvdo(7) for more information about VDO usage.

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

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

Controls whether deduplication is enabled or disabled for VDO volume.
    See lvmvdo(7) for more information about VDO usage.

Restricts the devices that are visible and accessible to the command.
    Devices not listed will appear to be missing. This option can be repeated, or accepts a comma separated list of devices. This overrides the devices file.

A file listing devices that LVM should use.
    The file must exist in /etc/lvm/devices/ and is managed with the lvmdevices(8) command. This overrides the lvm.conf(5) devices/devicesfile and devices/use_devicesfile settings.

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.

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

Specifies thin pool behavior when data space is exhausted.
    When yes, device-mapper will immediately return an error when a thin pool is full and an I/O request requires space. When no, device-mapper will queue these I/O requests for a period of time to allow the thin pool to be extended. Errors are returned if no space is available after the timeout. (Also see "dm_thin_pool" kernel module option no_space_timeout.) See lvmthin(7) for more information.

Override various checks, confirmations and protections.
    Use with extreme caution.

Display help text.

Specifies tunable kernel options for dm-integrity.
    See lvmraid(7) for more information.

Report progress at regular intervals.
    With a '+' prefix, the first check is delayed by the given number of seconds, allowing background operations to start before polling begins.

Record information in the systemd journal.
    This information is in addition to information enabled by the lvm.conf log/journal setting. command: record information about the command. output: record the default command output. debug: record full command debugging.

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

Display long help text.

An alias for --mergethin, --mergemirrors, or --mergesnapshot,
    depending on the type of LV.

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

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, 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.

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 information.

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

Specifies the type of mirror log for LVs with the "mirror" 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.

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(5) 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 number is subtracted from the current number of images. See lvmraid(7) for more information.

Specifies the name of a new LV.
    When unspecified, a default name of "lvol#" is generated, where # is a number generated by LVM.

Do not use the hints file to locate devices for PVs. A command may read
    more devices to find PVs when hints are not used. The command will still perform standard hint file invalidation where appropriate.

Disable locking. Use with caution, concurrent commands may produce
    incorrect results.

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

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.

Use VDO type volume for pool data volume.

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

Specifies the size of the new pool metadata LV.

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.

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

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

Enable or disable data integrity checksums for raid images.

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. Possible values: 512, 1024, 2048, 4096.

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 scattered write optimization.

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.

Size of each raid or mirror synchronization region.
    lvm.conf(5) activation/raid_region_size can be used to configure a default.

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 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.

Persistently sets (yes) or clears (no) the "activation skip" flag on an LV.
    An LV with this flag set is not activated unless the --ignoreactivationskip option is used by the activation command. This flag is set by default on new thin snapshot LVs. The flag is not applied to deactivation. The current value of the flag is indicated in the lvs lv_attr bits.

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

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.

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.

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.

Start polling an LV to continue processing a conversion.

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.

The amount of data that is written to one device before
    moving to the next in a striped LV.

Extracts the metadata LV from a pool and replaces it with another specified LV.
    The extracted LV is preserved 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).

Run in test mode. Commands will not update metadata.
    This is implemented by disabling all metadata writing but nevertheless returning success to the calling function. 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.

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

The name of a thin pool LV.

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 temporary state that allows the read-only detached image 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).

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 lvmraid(7). For thin provisioning (thin, thin-pool) see lvmthin(7). For performance caching (cache, cache-pool) see lvmcache(7). For copy-on-write snapshots (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.

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.

Perform an operation according to the policy configured in lvm.conf(5)
    or a profile.

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

Specifies tunable VDO options for VDO LVs.
    Use the form 'option=value' or 'option1=value option2=value', or repeat --vdosettings for each option being set. These settings override the default VDO behaviors. To remove vdosettings and revert to the default VDO behaviors, use --vdosettings 'default'. See lvmvdo(7) for more information.

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

Display version information.

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

Controls detection and subsequent wiping of signatures on new LVs.
    There is a prompt for each signature detected to confirm its wiping (unless --yes is used to override confirmations.) When not specified, signatures are wiped whenever zeroing is done (see --zero). This behaviour can be configured with lvm.conf(5) allocation/wipe_signatures_when_zeroing_new_lvs. If blkid wiping is used (lvm.conf(5) allocation/use_blkid_wiping) and LVM is compiled with blkid wiping support, then the blkid(8) library is used to detect the signatures (use blkid -k to list the signatures that are recognized). Otherwise, native LVM code is used to detect signatures (only MD RAID, swap and LUKS signatures are detected in this case.) The LV is not wiped if the read only flag is set.

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

For snapshots, this controls zeroing of the first 4 KiB 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.

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. LV1 indicates the LV must have a specific type, where the accepted LV types are listed. (raid represents 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 multiple 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 refer to 1024. The default input unit is specified by letter, followed by |UNIT. UNIT represents other possible input units: 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 substituted 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 LV1
    [ COMMON_OPTIONS ]

    LV1 types: raid

—

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

lvconvert LV1
    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: mirror

—

Convert LV to a thin LV, using the original LV as an external origin.

lvconvert --thinpool LV LV1
    [ --type thin ] (implied)
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: linear striped cache raid thin zero error

—

Convert LV to a thin LV, using LV as thin-pool data volume.

lvconvert LV1
    [ --type thin ] (implied)
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    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: linear striped cache raid vdo writecache zero error

—

Attach a cache pool to an LV.

lvconvert --cachepool LV LV1
    [ --type cache ] (implied)
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ COMMON_OPTIONS ]
    [ PV ... ]

    LV1 types: linear striped raid thin thinpool thinpooldata vdo vdopool vdopooldata zero error

—

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

lvconvert LV1
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ COMMON_OPTIONS ]

    LV1 types: linear striped raid thinpool

—

Convert LV to type vdopool (variant: use --type vdo-pool, existing data on LV will be erased).

lvconvert --vdopool LV1
    [ --type vdo-pool ] (implied)
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ ]
    [ COMMON_OPTIONS ]

    LV1 types: linear striped cache raid

—

Detach and delete a cache from an LV.

lvconvert LV1
    [ ]
    [ COMMON_OPTIONS ]

    LV1 types: cache thinpool vdopool writecache

—

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

lvconvert LV1
    [ ]
    [ COMMON_OPTIONS ]

    LV1 types: cachepool thinpool

—

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 VG|LV1|Tag ...
    [ ]
    [ COMMON_OPTIONS ]

    LV1 types: linear striped snapshot raid thin

—

Separate a COW snapshot from its origin LV.

lvconvert LV1
    [ COMMON_OPTIONS ]

    LV1 types: snapshot

—

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

lvconvert LV LV1
    [ --type snapshot ] (implied)
    [ ]
    [ ]
    [ COMMON_OPTIONS ]

    LV1 types: linear striped

—

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

lvconvert LV1
    [ COMMON_OPTIONS ]

    LV1 types: mirror raid

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

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 --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.
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 a thick LV into a thin-pool data volume and continue using this LV through thinLV and for the conversion set the pool metadata size to 1GiB.
lvconvert --type thin --poolmetadatasize 1G vg/lvol1

Convert an LV into a thin-pool with VDO deduplication and compression for storing its data.
lvconvert --type thin-pool --pooldatavdo y 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 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), lvmconfig(8), lvmdevices(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), vgimportdevices(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), blkdeactivate(8), lvmdump(8),

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

lvmsystemid(7), lvmreport(7), lvmcache(7), lvmraid(7), lvmthin(7), lvmvdo(7), lvmautoactivation(7)