lvm2/man/lvconvert.8.in

.TH LVCONVERT 8 "LVM TOOLS #VERSION#" "Red Hat, Inc" \" -*- nroff -*-
.SH NAME
lvconvert \- convert a logical volume from linear to mirror or snapshot
.SH SYNOPSIS
.B lvconvert
.BR \-m | \-\-mirrors
.I Mirrors
.RB [ \-\-mirrorlog
.RI { disk | core | mirrored }]
.RB [ \-\-corelog ]
.RB [ \-R | \-\-regionsize
.IR MirrorLogRegionSize ]
.RB [ \-\-type
.IR SegmentType ]
.RB [ \-A | \-\-alloc
.IR AllocationPolicy ]
.RB [ \-b | \-\-background ]
.RB [ \-f | \-\-force ]
.RB [ \-i | \-\-interval
.IR Seconds ]
.RB [ \-h | \-? | \-\-help ]
.RB [ \-\-stripes
.I Stripes
.RB [ \-I | \-\-stripesize
.IR StripeSize ]]
.RB [ \-\-noudevsync ]
.RB [ \-v | \-\-verbose ]
.RB [ \-y | \-\-yes ]
.RB [ \-\-version ]
.IR LogicalVolume [ Path ]
.RI [ PhysicalVolume [ Path ][ :PE [ -PE ]]...]
.sp
.B lvconvert \-\-splitmirrors \fIImages
.RB [ \-\-name
.IR SplitLogicalVolumeName ]
.RB [ \-\-trackchanges ]
.IR MirrorLogicalVolume [ Path ]
.RI [ SplittablePhysicalVolume [ Path ][ :PE [ -PE ]]...]
.sp
.B lvconvert
.BR \-s | \-\-snapshot
.RB [ \-c | \-\-chunksize
.IR ChunkSize [ bBsSkK ]]
.RB [ \-h | \-? | \-\-help ]
.RB [ \-\-noudevsync ]
.RB [ \-v | \-\-verbose ]
.RB [ \-Z | \-\-zero
.RI { y | n }]
.RB [ \-\-version ]
.IR OriginalLogicalVolume [ Path ]
.IR SnapshotLogicalVolume [ Path ]
.sp
.B lvconvert \-\-merge
.RB [ \-b | \-\-background ]
.RB [ \-i | \-\-interval
.IR Seconds ]
.RB [ \-h | \-? | \-\-help ]
.RB [ \-v | \-\-verbose ]
.RB [ \-\-version ]
.IR LogicalVolume [ Path ]...
.sp
.B lvconvert \-\-repair
.RB [ \-h | \-? | \-\-help ]
.RB [ \-\-stripes
.I Stripes
.RB [ \-I | \-\-stripesize
.IR StripeSize ]]
.RB [ \-v | \-\-verbose ]
.RB [ \-\-version ]
.IR LogicalVolume [ Path ]
.RI [ PhysicalVolume [ Path ]...]
.sp
.B lvconvert \-\-replace \fIPhysicalVolume
.RB [ \-h | \-? | \-\-help ]
.RB [ \-v | \-\-verbose ]
.RB [ \-\-version ]
.IR LogicalVolume [ Path ]
.RI [ PhysicalVolume [ Path ]...]
.sp
.B lvconvert \-\-thinpool
.IR ThinPoolLogicalVolume { Name | Path }
.RB [ \-c | \-\-chunksize
.IR ChunkSize [ bBsSkKmMgG ]]
.RB [ \-\-discards
.RI { ignore | nopassdown | passdown }]
.RB [[ \-\-poolmetadata
.IR ThinPoolMetadataLogicalVolume { Name | Path }]
|
.RB [ \-\-poolmetadatasize
.IR ThinPoolMetadataSize [ bBsSkKmMgG ]]
.RB [ \-r | \-\-readahead
.RI { ReadAheadSectors | auto | none }]
.RB [ \-\-stripes
.I Stripes
.RB [ \-I | \-\-stripesize
.IR StripeSize ]]]
.RB [ \-Z | \-\-zero
.RI { y | n }]
.RB [ \-h | \-? | \-\-help ]
.RB [ \-v | \-\-verbose ]
.RB [ \-\-version ]
.RI [ PhysicalVolume [ Path ][ :PE [ -PE ]]...]
.sp

.SH DESCRIPTION
lvconvert is used to change the segment type (i.e. linear, mirror, etc) or
characteristics of a logical volume.  For example, it can add or remove the
redundant images of a logical volume, change the log type of a mirror, or
designate a logical volume as a snapshot repository.
.br
If the conversion requires allocation of physical extents (for
example, when converting from linear to mirror) and you specify
one or more PhysicalVolumes (optionally with ranges of physical
extents), allocation of physical extents will be restricted to
these physical extents.  If the conversion frees physical extents
(for example, when converting from a mirror to a linear, or reducing
mirror legs) and you specify one or more PhysicalVolumes,
the freed extents come first from the specified PhysicalVolumes.
.SH OPTIONS
See \fBlvm\fP(8) for common options.
.br
Exactly one of 
.BR \-\-merge ", " \-\-mirrors ", " \-\-repair ", " \-\-replace
.RB ", " \-\-snapshot ", " \-\-splitmirrors " or " \-\-thinpool
arguments is required.
.TP
.BR \-m ", " \-\-mirrors " " \fIMirrors
Specifies the degree of the mirror you wish to create.
For example, "\fB-m 1\fP" would convert the original logical
volume to a mirror volume with 2-sides; that is, a
linear volume plus one copy.
.TP
.IR \fB\-\-mirrorlog " {" disk | core | mirrored }
Specifies the type of log to use.
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 - perhaps, for example, after every reboot.
Using "mirrored" will create a persistent log that is itself mirrored.
.TP
.B \-\-corelog
The optional argument \fB--corelog\fP is the same as specifying
\fB--mirrorlog core\fP.
.TP
.BR \-R ", " \-\-regionsize " " \fIMirrorLogRegionSize
A mirror is divided into regions of this size (in MB), and the mirror log
uses this granularity to track which regions are in sync.
.TP
.B \-\-type \fISegmentType
Used to convert a logical volume to another segment type or to explicitly state
the desired RAID1 segment type (\fImirror\fP or \fIraid1\fP) when converting
a linear logical volume to a mirror with the \fB-m\fP argument.
.TP
.BR \-b ", " \-\-background
Run the daemon in the background.
.TP
.BR \-i ", " \-\-interval " " \fISeconds
Report progress as a percentage at regular intervals.
.TP
.B \-\-noudevsync
Disable 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 LVM2 creates.
.TP
.B \-\-splitmirrors \fIImages
The number of redundant Images of a mirror to be split off and used
to form a new logical volume.  A name must be supplied for the
newly-split-off logical volume using the \fB\-\-name\fP argument, unless
the \fB\-\-trackchanges\fP argument is given.
.TP
.B \-n \fIName
The name to apply to a logical volume which has been split off from
a mirror logical volume.
.TP
.B \-\-trackchanges
Used with \fB\-\-splitmirrors\fP on a raid1 device, this tracks changes so
that the read-only detached image can be merged efficiently back into
the mirror later. Only the regions of the detatched device where
the data changed get resynchronized.

Please note that this feature is only supported with the new md-based mirror
implementation and not with the original device-mapper mirror implementation.
.TP
.B \-s, \-\-snapshot
Create a snapshot from existing logical volume using another
existing logical volume as its origin.
.TP
.BR \-c ", " \-\-chunksize " " \fIChunkSize [ \fIbBsSkKmMgG ]
Gives the size of chunk for snapshot and thin pool logical volumes.
For snapshots the value must be power of 2 between 4KiB and 512KiB
and the default value is 4.
For thin pools 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 128MB,
if the pool metadata size is not specified.
Older dm thin pool target version (<1.4) requires the value to be power of 2.
The newer version requires to be the multiple of 64KiB, however discard is
not supported for non power of 2 values.
Default unit is in kilobytes.
.TP
.BR \-\-discards " {" \fIignore | \fInopassdown | \fIpassdown }
Sets discards behavior for thin pool.
Default is \fIpassdown\fP.
.TP
.BR \-Z ", " \-\-zero " {" \fIy | \fIn }
Controls zeroing of the first KB of data in the snapshot.
If the volume is read-only the snapshot will not be zeroed.
For thin pool volumes it controls zeroing of provisioned blocks.
Note: Provisioning of large zeroed chunks impacts performance.
.TP
.B \-\-merge
Merges a snapshot into its origin volume or merges a raid1 image that has
been split from its mirror with \fB\-\-trackchanges\fP back into its mirror.

To check if your kernel supports the snapshot merge feature, look
for 'snapshot-merge' in the output
of \fBdmsetup targets\fP.  If both the origin and snapshot volume are not
open the merge will start immediately.  Otherwise, the merge will start
the first time either the origin or snapshot 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 logical volume will have the origin's name,
minor number and UUID.  While the merge is in progress, reads or writes to the
origin appear as they were directed to the snapshot being merged.  When the
merge finishes, the merged snapshot is removed.  Multiple snapshots may
be specified on the commandline or a @tag may be used to specify
multiple snapshots be merged to their respective origin.
.TP
.BR \-\-poolmetadata " " \fIThinPoolMetadataLogicalVolume { \fIName | \fIPath }
Specifies thin pool metadata logical volume.
The size should be in between 2MiB and 16GiB.
Thin pool is specified with the option
\fB\-\-thinpool\fP.
When the specified thin pool already exists,
the thin pool's metadata volume will be swapped with the given LV.
Properties of the thin pool like chunk size, discards or zero
are preserved by default in this case.
It can be useful for thin pool metadata repair or its offline resize,
since the content of metadata becomes accessible for
thin provisioning tools \fBthin_dump\fP(8) and \fBthin_restore\fP(8).
.TP
.BR \-\-poolmetadatasize " " \fIThinPoolMetadataSize [ \fIbBsSkKmMgG ]
Sets the size of thin pool's metadata logical volume,
if the pool metadata volume is undefined.
Thin pool is specified with the option
\fB\-\-thinpool\fP.
Supported value is in the range between 2MiB and 16GiB.
The default value is estimated with this formula
(Pool_LV_size / Pool_LV_chunk_size * 64b).
Default unit is megabytes.
.TP
.IR \fB\-r ", " \fB\-\-readahead " {" ReadAheadSectors | auto | none }
Sets read ahead sector count of thin pool metadata logical volume.
The default value is "auto" which allows the kernel to choose
a suitable value automatically.
"None" is equivalent to specifying zero.
.TP
.B \-\-repair
Repair a mirror after suffering a disk failure. The mirror will be brought back
into a consistent state.  By default, the original number of mirrors will be
restored if possible.  Specify \fB\-y\fP on the command line to skip
the prompts. Use \fB\-f\fP if you do not want any replacement.
Additionally, you may use \fB\-\-use-policies\fP to use the device
replacement policy specified in \fBlvm.conf\fP(5),
viz. activation/mirror_log_fault_policy or
activation/mirror_device_fault_policy.
.TP
.B \-\-replace \fIPhysicalVolume
Remove the specified device (\fIPhysicalVolume\fP) and replace it with one
that is available in the volume group or from the specific list provided.
This option is only available to RAID segment types
(e.g. "raid1", "raid5", etc).
.TP
.BR \-\-stripes " " \fIStripes
Gives the number of stripes.
This is equal to the number of physical volumes to scatter
the logical volume. This does not apply to existing allocated
space, only newly allocated space can be striped.
.TP
.BR \-I ", " \-\-stripesize " " \fIStripeSize
Gives the number of kilobytes for the granularity of the stripes.
.br
StripeSize must be 2^n (n = 2 to 9) for metadata in LVM1 format.
For metadata in LVM2 format, the stripe size may be a larger
power of 2 but must not exceed the physical extent size.
.TP
.IR \fB\-\-thinpool " " ThinPoolLogicalVolume { Name | Path }
Changes logical volume into a thin pool volume. The volume
will store the pool's data.
Thin pool metadata logical volume can be specified with the option
\fB\-\-poolmetadata\fP or allocated with \fB\-\-poolmetadatasize\fP.

.SH Examples
Converts the linear logical volume "vg00/lvol1" to a two-way mirror
logical volume:
.sp
.B lvconvert \-m1 vg00/lvol1

Converts the linear logical volume "vg00/lvol1" to a two-way RAID1
logical volume:
.sp
.B lvconvert \-\-type raid1 \-m1 vg00/lvol1

Converts a mirror with a disk log to a mirror with an in-memory log:
.sp
.B lvconvert \-\-mirrorlog core vg00/lvol1

Converts a mirror with an in-memory log to a mirror with a disk log:
.sp
.B lvconvert \-\-mirrorlog disk vg00/lvol1

Converts a mirror logical volume to a linear logical volume:
.sp
.B lvconvert \-m0 vg00/lvol1

Converts a mirror logical volume to a RAID1 logical volume with the same
number of images:
.sp
.B lvconvert \-\-type raid1 vg00/mirror_lv

Converts logical volume "vg00/lvol2" to snapshot of original volume
"vg00/lvol1":
.sp
.B lvconvert \-s vg00/lvol1 vg00/lvol2

Converts linear logical volume "vg00/lvol1" to a two-way mirror,
using physical extents /dev/sda:0-15 and /dev/sdb:0-15 for allocation
of new extents:
.sp
.B lvconvert \-m1 vg00/lvol1 /dev/sda:0-15 /dev/sdb:0-15

Converts mirror logical volume "vg00/lvmirror1" to linear, freeing physical
extents from /dev/sda:
.sp
.B lvconvert \-m0 vg00/lvmirror1 /dev/sda

Merges "vg00/lvol1_snap" into its origin:
.sp
.B lvconvert \-\-merge vg00/lvol1_snap

If "vg00/lvol1", "vg00/lvol2" and "vg00/lvol3" are all tagged with "some_tag"
each snapshot logical volume will be merged serially, 
e.g.: "vg00/lvol1", then "vg00/lvol2", then "vg00/lvol3".
If \-\-background were used it would start
all snapshot logical volume merges in parallel.
.sp
.B lvconvert \-\-merge @some_tag

Extracts one image from the mirror, making it a new logical volume named
"lv_split".  The mirror the image is extracted from is reduced accordingly.
If it was a 2-way mirror (created with '-m 1'), then the resulting original
volume will be linear.
.sp
.B lvconvert \-\-splitmirrors 1 \-\-name lv_split vg00/lvmirror1

A mirrored logical volume created with \-\-type raid1 can use the
\-\-trackchanges argument when splitting off an image.
Detach one image from the mirrored logical volume lv_raid1 as a separate
read-only device and track the changes made to the mirror while it is detached.
The split-off device has a name of the form lv_raid1_rimage_N, where N is
a number, and it cannot be renamed.
.sp
.B lvconvert \-\-splitmirrors 1 \-\-trackchanges vg00/lv_raid1

Merge an image that was detached temporarily from its mirror with
the \-\-trackchanges argument back into its original mirror and
bring its contents back up-to-date.
.sp
.B lvconvert \-\-merge vg00/lv_raid1_rimage_1

Replaces the physical volume "/dev/sdb1" in the RAID1 logical volume "my_raid1"
with the specified physical volume "/dev/sdf1".  Had the argument "/dev/sdf1"
been left out, lvconvert would attempt to find a suitable device from those
available in the volume group.
.sp
.B lvconvert \-\-replace /dev/sdb1 vg00/my_raid1 /dev/sdf1

.SH SEE ALSO
.BR lvm (8),
.BR vgcreate (8),
.BR lvremove (8),
.BR lvrename (8),
.BR lvextend (8),
.BR lvreduce (8),
.BR lvdisplay (8),
.BR lvscan (8),
.BR thin_dump(8),
.BR thin_restore(8)