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83978cdec8
Do a better job explaining the '--stripes/-i' option to lvcreate when it comes to RAID 4/5/6. The extra devices needed for parity are implicitly added to the argument given. So a 5-device RAID6 logical volume is created with '-i 3' - indicating 3 stripes plus the implicit 2 devices needed for RAID6.
394 lines
15 KiB
Groff
394 lines
15 KiB
Groff
.TH LVCREATE 8 "LVM TOOLS #VERSION#" "Sistina Software UK" \" -*- nroff -*-
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.SH NAME
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lvcreate \- create a logical volume in an existing volume group
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.SH SYNOPSIS
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.B lvcreate
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.RB [ \-\-addtag
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.IR Tag ]
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.RB [ \-\-alloc
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.IR AllocationPolicy ]
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.RB [ \-a | \-\-activate
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.RI [ a | e | l ]{ y | n }]
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.RB [ \-A | \-\-autobackup
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.RI { y | n }]
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.RB [ \-C | \-\-contiguous
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.RI { y | n }]
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.RB [ \-d | \-\-debug ]
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.RB [ \-h | \-? | \-\-help ]
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.RB [ \-\-noudevsync ]
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.RB [ \-\-ignoremonitoring ]
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.RB [ \-\-monitor
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.RI { y | n }]
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.RB [ \-i | \-\-stripes
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.IR Stripes
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.RB [ \-I | \-\-stripesize
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.IR StripeSize ]]
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.RB {[ \-l | \-\-extents
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.IR LogicalExtentsNumber [ % { VG | PVS | FREE }]
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.BR \-L | \-\-size
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.IR LogicalVolumeSize [ bBsSkKmMgGtTpPeE ]]
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.BR \-V | \-\-virtualsize
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.IR VirtualSize [ bBsSkKmMgGtTpPeE ]}
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.RB [ \-M | \-\-persistent
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.RI { y | n }]
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.RB [ \-\-minor
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.IR minor ]
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.RB [ \-m | \-\-mirrors
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.IR Mirrors
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.RB [ \-\-nosync ]
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.RB [ \-\-mirrorlog
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.RI { disk | core | mirrored }
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.BR \-\-corelog ]
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.RB [ \-R | \-\-regionsize
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.IR MirrorLogRegionSize ]]
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.RB [ \-n | \-\-name
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.IR LogicalVolume { Name | Path }]
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.RB [ \-p | \-\-permission
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.RI { r | rw }]
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.RB [ \-r | \-\-readahead
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.RI { ReadAheadSectors | auto | none }]
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.RB [ \-t | \-\-test ]
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.RB [ \-T | \-\-thin
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.RB [ \-c | \-\-chunksize
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.IR ChunkSize [ bBsSkKmMgG ]]
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.RB [ \-\-discards
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.RI { ignore | nopassdown | passdown }]
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.RB [ \-\-poolmetadatasize
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.IR ThinPoolMetadataSize [ bBsSkKmMgG ]]]
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.RB [ \-\-thinpool
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.IR ThinPoolLogicalVolume { Name | Path }]
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.RB [ \-\-type
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.IR SegmentType ]
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.RB [ \-v | \-\-verbose ]
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.RB [ \-Z | \-\-zero
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.RI { y | n }]
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.IR VolumeGroup { Name | Path }[/ ThinPoolLogicalVolumeName ]
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.RI [ PhysicalVolumePath [ :PE [ -PE ]]...]
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.br
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.B lvcreate
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.RB [ \-l | \-\-extents
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.IR LogicalExtentsNumber [ % { VG | FREE | ORIGIN }]
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.BR \-L | \-\-size
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.IR LogicalVolumeSize [ bBsSkKmMgGtTpPeE ]]
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.RB [ \-c | \-\-chunksize
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.IR ChunkSize [ bBsSkK ]]
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.RB [ \-\-noudevsync ]
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.RB [ \-\-ignoremonitoring ]
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.RB [ \-\-monitor " {" \fIy | \fIn }]
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.RB [ \-n | \-\-name
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.IR SnapshotLogicalVolume { Name | Path }]
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.BR \-s | \-\-snapshot
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.RI {[ VolumeGroup { Name | Path }/] OriginalLogicalVolumeName
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.BR \-V | \-\-virtualsize
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.IR VirtualSize [ bBsSkKmMgGtTpPeE ]}
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.br
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.SH DESCRIPTION
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lvcreate creates a new logical volume in a volume group (see
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.BR vgcreate "(8), " vgchange (8))
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by allocating logical extents from the free physical extent pool
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of that volume group. If there are not enough free physical extents then
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the volume group can be extended (see
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.BR vgextend (8))
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with other physical volumes or by reducing existing logical volumes
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of this volume group in size (see
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.BR lvreduce (8)).
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If you specify one or more PhysicalVolumes, allocation of physical
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extents will be restricted to these volumes.
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.br
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.br
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The second form supports the creation of snapshot logical volumes which
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keep the contents of the original logical volume for backup purposes.
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.SH OPTIONS
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See
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.BR lvm (8)
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for common options.
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.TP
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.IR \fB\-a ", " \fB\-\-activate " {" y | ay | n | ey | en | ly | ln }
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Controls the availability of the Logical Volumes for immediate use after
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the command finishes running.
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By default, new Logical Volumes are activated (\fB-a\fIy\fR).
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If it is possible technically, \fB-a\fIn\fR will leave the new Logical
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Volume inactive. But for example, snapshots can only be created
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in the active state so \fB\-a\fIn\fR cannot be used with \fB\-\-snapshot\fP.
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Normally the \fB\-\-zero n\fP argument has to be supplied too because
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zeroing (the default behaviour) also requires activation.
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If autoactivation option is used (\fB\-a\fIay\fR), the logical volume is
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activated only if it matches an item in the activation/auto_activation_volume_list
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set in lvm.conf. For autoactivated logical volumes, \fB\-\-zero n\fP is
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always assumed and it can't be overridden. If clustered locking is enabled,
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\fB\-a\fIey\fR will activate exclusively on one node and \fB\-a\fIly\fR will
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activate only on the local node.
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.TP
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.BR \-c ", " \-\-chunksize " " \fIChunkSize [ \fIbBsSkKmMgG ]
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Gives the size of chunk for snapshot and thin pool logical volumes.
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For snapshots the value must be power of 2 between 4KiB and 512KiB
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and the default value is 4.
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For thin pools the value must be between 64KiB and
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1GiB and the default value starts with 64 and scales
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up to fit the pool metadata size within 128MB,
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if the pool metadata size is not specified.
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Older dm thin pool target version (<1.4) requires the value to be power of 2.
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The newer version requires to be the multiple of 64KiB, however discard is
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not supported for non power of 2 values.
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Default unit is in kilobytes.
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.TP
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.BR \-C ", " \-\-contiguous " {" \fIy | \fIn }
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Sets or resets the contiguous allocation policy for
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logical volumes. Default is no contiguous allocation based
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on a next free principle.
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.TP
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.BR \-\-discards " {" \fIignore | \fInopassdown | \fIpassdown }
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Set discards behavior for thin pool.
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Default is \fIpassdown\fP.
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.TP
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.BR \-i ", " \-\-stripes " " \fIStripes
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Gives the number of stripes.
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This is equal to the number of physical volumes to scatter
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the logical volume. When creating a RAID 4/5/6 logical volume,
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the extra devices which are necessary for parity are
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internally accounted for. Specifying '\-i 3' would use 3 devices
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for striped logical volumes, 4 devices for RAID 4/5, and 5 devices
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for RAID 6.
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.TP
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.BR \-I ", " \-\-stripesize " " \fIStripeSize
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Gives the number of kilobytes for the granularity of the stripes.
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.br
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StripeSize must be 2^n (n = 2 to 9) for metadata in LVM1 format.
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For metadata in LVM2 format, the stripe size may be a larger
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power of 2 but must not exceed the physical extent size.
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.TP
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.IR \fB\-l ", " \fB\-\-extents " " LogicalExtentsNumber [ % { VG | PVS | FREE | ORIGIN }]
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Gives the number of logical extents to allocate for the new
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logical volume.
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The number can also be expressed as a percentage of the total space
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in the Volume Group with the suffix \fI%VG\fR, as a percentage of the
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remaining free space in the Volume Group with the suffix \fI%FREE\fR, as a
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percentage of the remaining free space for the specified
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PhysicalVolume(s) with the suffix \fI%PVS\fR, or (for a snapshot) as a
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percentage of the total space in the Origin Logical Volume with the
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suffix \fI%ORIGIN\fR.
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.TP
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.IR \fB\-L ", " \fB\-\-size " " LogicalVolumeSize [ bBsSkKmMgGtTpPeE ]
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Gives the size to allocate for the new logical volume.
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A size suffix of \fIK\fR for kilobytes, \fIM\fR for megabytes,
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\fIG\fR for gigabytes, \fIT\fR for terabytes, \fIP\fR for petabytes
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or \fIE\fR for exabytes is optional.
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.br
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Default unit is megabytes.
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.TP
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.B \-\-minor \fIminor
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Set the minor number.
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.TP
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.IR \fB\-M ", " \fB\-\-persistent " {" y | n }
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Set to y to make the minor number specified persistent.
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.TP
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.BR \-m ", " \-\-mirrors " " \fIMirrors
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Creates a mirrored logical volume with Mirrors copies. For example,
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specifying "-m 1" would result in a mirror with two-sides; that is, a
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linear volume plus one copy.
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Specifying the optional argument --nosync will cause the creation
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of the mirror to skip the initial resynchronization. Any data written
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afterwards will be mirrored, but the original contents will not be
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copied. This is useful for skipping a potentially long and resource
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intensive initial sync of an empty device.
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The optional argument --mirrorlog specifies the type of log to be used.
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The default is disk, which is persistent and requires
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a small amount of storage space, usually on a separate device from the
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data being mirrored. Using core means the mirror is regenerated
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by copying the data from the first device again each time the
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device is activated, for example, after every reboot. Using "mirrored"
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will create a persistent log that is itself mirrored.
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The optional argument --corelog is equivalent to --mirrorlog core.
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.TP
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.IR \fB\-n ", " \fB\-\-name " " LogicalVolume { Name | Path }
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The name for the new logical volume.
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.br
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Without this option a default names of "lvol#" will be generated where
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# is the LVM internal number of the logical volume.
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.TP
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.B \-\-noudevsync
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Disable udev synchronisation. The
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process will not wait for notification from udev.
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It will continue irrespective of any possible udev processing
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in the background. You should only use this if udev is not running
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or has rules that ignore the devices LVM2 creates.
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.TP
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.BR \-\-monitor " {" \fIy | \fIn }
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Start or avoid monitoring a mirrored or snapshot logical volume with
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dmeventd, if it is installed.
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If a device used by a monitored mirror reports an I/O error,
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the failure is handled according to
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\fBmirror_image_fault_policy\fP and \fBmirror_log_fault_policy\fP
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set in \fBlvm.conf\fP.
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.TP
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.B \-\-ignoremonitoring
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Make no attempt to interact with dmeventd unless \-\-monitor
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is specified.
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.TP
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.BR \-p ", " \-\-permission " {" \fIr | \fIrw }
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Set access permissions to read only or read and write.
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.br
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Default is read and write.
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.TP
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.IR \fB\-\-poolmetadatasize " " ThinPoolMetadataSize [ bBsSkKmMgG ]
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Set the size of thin pool's metadata logical volume.
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Supported value is in range between 2MiB and 16GiB.
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Default value is (Pool_LV_size / Pool_LV_chunk_size * 64b).
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Default unit is megabytes.
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.TP
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.IR \fB\-r ", " \fB\-\-readahead " {" ReadAheadSectors | auto | none }
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Set read ahead sector count of this logical volume.
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For volume groups with metadata in lvm1 format, this must
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be a value between 2 and 120.
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The default value is "auto" which allows the kernel to choose
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a suitable value automatically.
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"None" is equivalent to specifying zero.
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.TP
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.BR \-R ", " \-\-regionsize " " \fIMirrorLogRegionSize
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A mirror is divided into regions of this size (in MB), and the mirror log
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uses this granularity to track which regions are in sync.
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.TP
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.IR \fB\-s ", " \fB\-\-snapshot " " OriginalLogicalVolume { Name | Path }
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Create a snapshot logical volume (or snapshot) for an existing, so called
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original logical volume (or origin).
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Snapshots provide a 'frozen image' of the contents of the origin
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while the origin can still be updated. They enable consistent
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backups and online recovery of removed/overwritten data/files.
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Thin snapshot is created when the origin is a thin volume and
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the size is not specified. Thin snapshot shares same blocks within
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the thin pool volume.
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The snapshot with the specified size does not need the same amount of
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storage the origin has. In a typical scenario, 15-20% might be enough.
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In case the snapshot runs out of storage, use
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.BR lvextend (8)
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to grow it. Shrinking a snapshot is supported by
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.BR lvreduce (8)
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as well. Run
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.BR lvdisplay (8)
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on the snapshot in order to check how much data is allocated to it.
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Note that a small amount of the space you allocate to the snapshot is
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used to track the locations of the chunks of data, so you should
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allocate slightly more space than you actually need and monitor the
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rate at which the snapshot data is growing so you can avoid running out
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of space.
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.TP
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.IR \fB\-T ", " \fB\-\-thin ", " \fB\-\-thinpool " " ThinPoolLogicalVolume { Name | Path }
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Creates thin pool or thin logical volume or both.
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Specifying the optional argument \fB\-\-size\fP will cause the creation of
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the thin pool logical volume.
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Specifying the optional argument \fB\-\-virtualsize\fP will cause
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the creation of the thin logical volume from given thin pool volume.
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Specifying both arguments will cause the creation of both
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thin pool and thin volume using this pool.
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Requires device mapper kernel driver for thin provisioning
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from kernel 3.2 or newer.
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.TP
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.B \-\-type \fISegmentType
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Create a logical volume that uses the specified segment type
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(e.g. "raid5", "mirror", "snapshot", "thin", "thin-pool").
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Many segment types have a
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commandline switch alias that will enable their use
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(\fB\-s\fP is an alias for \fB\-\-type snapshot\fP).
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However, this argument must be used when no existing
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commandline switch alias is available for the desired type,
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as is the case with
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.IR error ", " zero ", " raid1 ", " raid10 ", " raid4 ", " raid5 " or " raid6 .
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.TP
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.BR \-V ", " \-\-virtualsize " " \fIVirtualSize [ \fIbBsSkKmMgGtTpPeE ]
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Create a sparse device of the given size (in MB by default) using a snapshot
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or thinly provisioned device when thin pool is specified.
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Anything written to the device will be returned when reading from it.
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Reading from other areas of the device will return blocks of zeros.
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Virtual snapshot is implemented by creating a hidden virtual device of the
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requested size using the zero target. A suffix of _vorigin is used for
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this device.
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.TP
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.BR \-Z ", " \-\-zero " {" \fIy | \fIn }
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Controls zeroing of the first KB of data in the new logical volume.
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.br
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Default is yes.
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.br
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Volume will not be zeroed if read only flag is set.
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.br
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Snapshot volumes are zeroed always.
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.br
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Warning: trying to mount an unzeroed logical volume can cause the system to
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hang.
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.SH Examples
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Creates a striped logical volume with 3 stripes, a stripesize of 8KB
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and a size of 100MB in the volume group named vg00.
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The logical volume name will be chosen by lvcreate:
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.sp
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.B lvcreate \-i 3 \-I 8 \-L 100M vg00
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Creates a mirror logical volume with 2 sides with a useable size of 500 MiB.
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This operation would require 3 devices (or option --alloc anywhere) - two
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for the mirror devices and one for the disk log:
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.sp
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.B lvcreate \-m1 \-L 500M vg00
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Creates a mirror logical volume with 2 sides with a useable size of 500 MiB.
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This operation would require 2 devices - the log is "in-memory":
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.sp
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.B lvcreate \-m1 \-\-mirrorlog core \-L 500M vg00
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Creates a snapshot logical volume named /dev/vg00/snap which has access to the
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contents of the original logical volume named /dev/vg00/lvol1
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at snapshot logical volume creation time. If the original logical volume
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contains a file system, you can mount the snapshot logical volume on an
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arbitrary directory in order to access the contents of the filesystem to run
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a backup while the original filesystem continues to get updated:
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.sp
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.B lvcreate \-\-size 100m \-\-snapshot \-\-name snap /dev/vg00/lvol1
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Creates a sparse device named /dev/vg1/sparse of size 1TiB with space for just
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under 100MiB of actual data on it:
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.sp
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.B lvcreate \-\-virtualsize 1T \-\-size 100M \-\-snapshot \-\-name sparse vg1
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Creates a linear logical volume "vg00/lvol1" using physical extents
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/dev/sda:0-7 and /dev/sdb:0-7 for allocation of extents:
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.sp
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.B lvcreate \-L 64M -n lvol1 vg00 /dev/sda:0\-7 /dev/sdb:0\-7
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Creates a 5GiB RAID5 logical volume "vg00/my_lv", with 3 stripes (plus
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a parity drive for a total of 4 devices) and a stripesize of 64KiB:
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.sp
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.B lvcreate \-\-type raid5 \-L 5G \-i 3 \-I 64 \-n my_lv vg00
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Creates a 5GiB RAID10 logical volume "vg00/my_lv", with 2 stripes on
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2 2-way mirrors. Note that the '-i' and '-m' arguments behave differently.
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The '-i' specifies the number of stripes. The '-m' specifies the number of
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.B additional
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copies.
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.sp
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.B lvcreate \-\-type raid10 \-L 5G \-i 2 \-m 1 \-n my_lv vg00
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Creates 100MiB pool logical volume for thin provisioning
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build with 2 stripes 64KiB and chunk size 256KiB together with
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1TiB thin provisioned logical volume "vg00/thin_lv":
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.sp
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.B lvcreate \-i 2 \-I 64 \-c 256 \-L100M \-T vg00/pool \-V 1T \-\-name thin_lv
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.SH SEE ALSO
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.BR lvm (8),
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.BR vgcreate (8),
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.BR lvchange (8),
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.BR lvremove (8),
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.BR lvrename (8)
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.BR lvextend (8),
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.BR lvreduce (8),
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.BR lvdisplay (8),
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.BR lvscan (8)
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