Refer to details of snapshot of raid problem.

[lvm2.git] / man / lvcreate.8.in

.TH LVCREATE 8 "LVM TOOLS #VERSION#" "Sistina Software UK" \" -*- nroff -*-
.SH NAME
lvcreate \- create a logical volume in an existing volume group
.SH SYNOPSIS
.B lvcreate
.RB [ \-\-addtag
.IR Tag ]
.RB [ \-\-alloc
.IR AllocationPolicy ]
.RB [ \-a | \-\-available
.RI [ e | l ]{ y | n }]
.RB [ \-A | \-\-autobackup
.RI { y | n }]
.RB [ \-C | \-\-contiguous
.RI { y | n }]
.RB [ \-d | \-\-debug ]
.RB [ \-h | \-? | \-\-help ]
.RB [ \-\-noudevsync ]
.RB [ \-\-ignoremonitoring ]
.RB [ \-\-monitor
.RI { y | n }]
.RB [ \-i | \-\-stripes
.IR Stripes
.RB [ \-I | \-\-stripesize
.IR StripeSize ]]
.RB {[ \-l | \-\-extents
.IR LogicalExtentsNumber [ % { VG | PVS | FREE }]
|
.BR \-L | \-\-size
.IR LogicalVolumeSize [ bBsSkKmMgGtTpPeE ]]
|
.BR \-V | \-\-virtualsize
.IR VirtualSize [ bBsSkKmMgGtTpPeE ]}
.RB [ \-M | \-\-persistent
.RI { y | n }]
.RB [ \-\-minor
.IR minor ]
.RB [ \-m | \-\-mirrors
.IR Mirrors
.RB [ \-\-nosync ]
.RB [ \-\-mirrorlog
.RI { disk | core | mirrored }
|
.BR \-\-corelog ]
.RB [ \-R | \-\-regionsize
.IR MirrorLogRegionSize ]]
.RB [ \-n | \-\-name
.IR LogicalVolume { Name | Path }]
.RB [ \-p | \-\-permission
.RI { r | rw }]
.RB [ \-r | \-\-readahead
.RI { ReadAheadSectors | auto | none }]
.RB [ \-t | \-\-test ]
.RB [ \-T | \-\-thin
.RB [ \-c | \-\-chunksize
.IR ChunkSize ]
.RB [ \-\-poolmetadatasize
.IR MetadataSize [ bBsSkKmMgG ]]]
.RB [ \-\-thinpool
.IR ThinPoolLogicalVolume { Name | Path }]
.RB [ \-\-type
.IR SegmentType ]
.RB [ \-v | \-\-verbose ]
.RB [ \-Z | \-\-zero
.RI { y | n }]
.IR VolumeGroup { Name | Path }[/ ThinPoolLogicalVolumeName ]
.RI [ PhysicalVolumePath [ :PE [ -PE ]]...]
.br

.B lvcreate
.RB [ \-l | \-\-extents
.IR LogicalExtentsNumber [ % { VG | FREE | ORIGIN }]
|
.BR \-L | \-\-size
.IR LogicalVolumeSize [ bBsSkKmMgGtTpPeE ]]
.RB [ \-c | \-\-chunksize
.IR ChunkSize ]
.RB [ \-\-noudevsync ]
.RB [ \-\-ignoremonitoring ]
.RB [ \-\-monitor " {" \fIy | \fIn }]
.RB [ \-n | \-\-name
.IR SnapshotLogicalVolume { Name | Path }]
.BR \-s | \-\-snapshot
.RI {[ VolumeGroup { Name | Path }/] OriginalLogicalVolumeName
.BR \-V | \-\-virtualsize
.IR VirtualSize [ bBsSkKmMgGtTpPeE ]}
.br

.SH DESCRIPTION
lvcreate creates a new logical volume in a volume group (see
.BR vgcreate "(8), " vgchange (8))
by allocating logical extents from the free physical extent pool
of that volume group.  If there are not enough free physical extents then
the volume group can be extended (see
.BR vgextend (8))
with other physical volumes or by reducing existing logical volumes
of this volume group in size (see
.BR lvreduce (8)).
If you specify one or more PhysicalVolumes, allocation of physical
extents will be restricted to these volumes.
.br
.br
The second form supports the creation of snapshot logical volumes which
keep the contents of the original logical volume for backup purposes.
.SH OPTIONS
See
.BR lvm (8)
for common options.
.TP
.IR \fB\-a ", " \fB\-\-available " {" y | n | ey | en | ly | ln }
Controls the availability of the Logical Volumes for immediate use after
the command finishes running.
By default, new Logical Volumes are activated automatically (\fB-a\fIy\fR).
If it is possible technically, \fB-a\fIn\fR will leave the new Logical
Volume inactive. But for example, snapshots can only be created
in the active state so \fB\-a\fIn\fR cannot be used with \fB\-\-snapshot\fP.
Normally the \fB\-\-zero n\fP argument has to be supplied too because
zeroing (the default behaviour) also requires activation.
If clustered locking is enabled, \fB\-a\fIey\fR will activate exclusively
on one node and \fB\-a\fIly\fR will activate only on the local node.
.TP
.BR \-c ", " \-\-chunksize " " \fIChunkSize
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 power of 2 between 64KiB and
1048576KiB and the default value starts with 64 and scales
up to fit the pool metadata size within 128MB,
if the poolmetadata size is not specified.
Default unit is in kilobytes.
.TP
.BR \-C ", " \-\-contiguous " {" \fIy | \fIn }
Sets or resets the contiguous allocation policy for
logical volumes. Default is no contiguous allocation based
on a next free principle.
.TP
.BR \-i ", " \-\-stripes " " \fIStripes
Gives the number of stripes.
This is equal to the number of physical volumes to scatter
the logical volume.
.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\-l ", " \fB\-\-extents " " LogicalExtentsNumber [ % { VG | PVS | FREE | ORIGIN }]
Gives the number of logical extents to allocate for the new
logical volume.
The number can also be expressed as a percentage of the total space
in the Volume Group with the suffix \fI%VG\fR, as a percentage of the
remaining free space in the Volume Group with the suffix \fI%FREE\fR, as a
percentage of the remaining free space for the specified
PhysicalVolume(s) with the suffix \fI%PVS\fR, or (for a snapshot) as a
percentage of the total space in the Origin Logical Volume with the
suffix \fI%ORIGIN\fR.
.TP
.IR \fB\-L ", " \fB\-\-size " " LogicalVolumeSize [ bBsSkKmMgGtTpPeE ]
Gives the size to allocate for the new logical volume.
A size suffix of \fIK\fR for kilobytes, \fIM\fR for megabytes,
\fIG\fR for gigabytes, \fIT\fR for terabytes, \fIP\fR for petabytes
or \fIE\fR for exabytes is optional.
.br
Default unit is megabytes.
.TP
.B \-\-minor \fIminor
Set the minor number.
.TP
.IR \fB\-M ", " \fB\-\-persistent " {" y | n }
Set to y to make the minor number specified persistent.
.TP
.BR \-m ", " \-\-mirrors " " \fIMirrors
Creates a mirrored logical volume with Mirrors copies.  For example,
specifying "-m 1" would result in a mirror with two-sides; that is, a
linear volume plus one copy.

Specifying the optional argument --nosync will cause the creation
of the mirror to skip the initial resynchronization.  Any data written
afterwards will be mirrored, but the original contents will not be
copied.  This is useful for skipping a potentially long and resource
intensive initial sync of an empty device.

The optional argument --mirrorlog specifies the type of log to be used.
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.  Using core means the mirror is regenerated
by copying the data from the first device again each time the
device is activated, for example, after every reboot.  Using "mirrored"
will create a persistent log that is itself mirrored.

The optional argument --corelog is equivalent to --mirrorlog core.

.TP
.IR \fB\-n ", " \fB\-\-name " " LogicalVolume { Name | Path }
The name for the new logical volume.
.br
Without this option a default names of "lvol#" will be generated where
# is the LVM internal number of the logical volume.
.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
.BR \-\-monitor " {" \fIy | \fIn }
Start or avoid monitoring a mirrored or snapshot logical volume with
dmeventd, if it is installed.
If a device used by a monitored mirror reports an I/O error,
the failure is handled according to
\fBmirror_image_fault_policy\fP and \fBmirror_log_fault_policy\fP
set in \fBlvm.conf\fP.
.TP
.B \-\-ignoremonitoring
Make no attempt to interact with dmeventd unless \-\-monitor
is specified.
.TP
.BR \-p ", " \-\-permission " {" \fIr | \fIrw }
Set access permissions to read only or read and write.
.br
Default is read and write.
.TP
.IR \fB\-\-poolmetadatasize " " MetadataSize [ bBsSkKmMgG ]
Set the size of thin pool's metadata logical volume.
Supported value is in range between 2MiB and 16GiB.
Default value is  (Pool_LV_size / Pool_LV_chunk_size * 64b).
Default unit is megabytes.
.TP
.IR \fB\-r ", " \fB\-\-readahead " {" ReadAheadSectors | auto | none }
Set read ahead sector count of this logical volume.
For volume groups with metadata in lvm1 format, this must
be a value between 2 and 120.
The default value is "auto" which allows the kernel to choose
a suitable value automatically.
"None" is equivalent to specifying zero.
.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
.IR \fB\-s ", " \fB\-\-snapshot " " OriginalLogicalVolume { Name | Path }
Create a snapshot logical volume (or snapshot) for an existing, so called
original logical volume (or origin).
Snapshots provide a 'frozen image' of the contents of the origin
while the origin can still be updated. They enable consistent
backups and online recovery of removed/overwritten data/files.
Thin snapshot is created when the origin is a thin volume and
the size is not specified. Thin snapshot shares same blocks within
the thin pool volume.
The snapshot with the specified size does not need the same amount of
storage the origin has. In a typical scenario, 15-20% might be enough.
In case the snapshot runs out of storage, use
.BR lvextend (8)
to grow it. Shrinking a snapshot is supported by
.BR lvreduce (8)
as well. Run
.BR lvdisplay (8)
on the snapshot in order to check how much data is allocated to it.
Note that a small amount of the space you allocate to the snapshot is
used to track the locations of the chunks of data, so you should
allocate slightly more space than you actually need and monitor the
rate at which the snapshot data is growing so you can avoid running out
of space.
.TP
.IR \fB\-T ", " \fB\-\-thin ", " \fB\-\-thinpool " " ThinPoolLogicalVolume { Name | Path }
Creates thin pool or thin logical volume or both.
Specifying the optional argument \fB\-\-size\fP will cause the creation of
the thin pool logical volume.
Specifying the optional argument \fB\-\-virtualsize\fP will cause
the creation of the thin logical volume from given thin pool volume.
Specifying both arguments will cause the creation of both
thin pool and thin volume using this pool.
Requires device mapper kernel driver for thin provisioning
from kernel 3.2 or newer.
.TP
.B \-\-type \fISegmentType
Create a logical volume that uses the specified segment type
(e.g. "raid5", "mirror", "snapshot", "thin", "thin-pool").
Many segment types have a
commandline switch alias that will enable their use
(\fB\-s\fP is an alias for \fB\-\-type snapshot\fP).
However, this argument must be used when no existing
commandline switch alias is available for the desired type,
as is the case with
.IR error ", " zero ", " raid1 ", " raid4 ", " raid5 " or " raid6 .
.TP
.BR \-V ", " \-\-virtualsize " " \fIVirtualSize [ \fIbBsSkKmMgGtTpPeE ]
Create a sparse device of the given size (in MB by default) using a snapshot
or thinly provisioned device when thin pool is specified.
Anything written to the device will be returned when reading from it.
Reading from other areas of the device will return blocks of zeros.
Virtual snapshot is implemented by creating a hidden virtual device of the
requested size using the zero target.  A suffix of _vorigin is used for
this device.
.TP
.BR \-Z ", " \-\-zero " {" \fIy | \fIn }
Controls zeroing of the first KB of data in the new logical volume.
.br
Default is yes.
.br
Volume will not be zeroed if read only flag is set.
.br
Snapshot volumes are zeroed always.

.br
Warning: trying to mount an unzeroed logical volume can cause the system to
hang.
.SH Examples
Creates a striped logical volume with 3 stripes, a stripesize of 8KB
and a size of 100MB in the volume group named vg00.
The logical volume name will be chosen by lvcreate:
.sp
.B lvcreate \-i 3 \-I 8 \-L 100M vg00

Creates a mirror logical volume with 2 sides with a useable size of 500 MiB.
This operation would require 3 devices (or option --alloc anywhere) - two
for the mirror devices and one for the disk log:
.sp
.B lvcreate \-m1 \-L 500M vg00

Creates a mirror logical volume with 2 sides with a useable size of 500 MiB.
This operation would require 2 devices - the log is "in-memory":
.sp
.B lvcreate \-m1 \-\-mirrorlog core \-L 500M vg00

Creates a snapshot logical volume named /dev/vg00/snap which has access to the
contents of the original logical volume named /dev/vg00/lvol1
at snapshot logical volume creation time. If the original logical volume
contains a file system, you can mount the snapshot logical volume on an
arbitrary directory in order to access the contents of the filesystem to run
a backup while the original filesystem continues to get updated:
.sp
.B lvcreate \-\-size 100m \-\-snapshot \-\-name snap /dev/vg00/lvol1

Creates a sparse device named /dev/vg1/sparse of size 1TiB with space for just
under 100MiB of actual data on it:
.sp
.B lvcreate \-\-virtualsize 1T \-\-size 100M \-\-snapshot \-\-name sparse vg1

Creates a linear logical volume "vg00/lvol1" using physical extents
/dev/sda:0-7 and /dev/sdb:0-7 for allocation of extents:
.sp
.B lvcreate \-L 64M -n lvol1 vg00 /dev/sda:0\-7 /dev/sdb:0\-7

Creates a 5GiB RAID5 logical volume "vg00/my_lv", with 3 stripes (plus
a parity drive for a total of 4 devices) and a stripesize of 64KiB:
.sp
.B lvcreate \-\-type raid5 \-L 5G \-i 3 \-I 64 \-n my_lv vg00

Creates 100MiB pool logical volume for thin provisioning
build with 2 stripes 64KiB and chunk size 128KiB together with
1TiB thin provisioned logical volume "vg00/thin_lv":
.sp
.B lvcreate \-i 2 \-I 64 \-c 256 \-L100M \-T vg00/pool \-V 1T \-\-name thin_lv

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