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NetBSD 6.1.5 - man page for lvcreate (netbsd section 8)

LVCREATE(8)									      LVCREATE(8)

NAME
       lvcreate - create a logical volume in an existing volume group

SYNOPSIS
       lvcreate  [--addtag Tag] [--alloc AllocationPolicy] [-A|--autobackup y|n] [-C|--contiguous
       y|n]  [-d|--debug]  [-h|-?|--help]  [-i|--stripes  Stripes  [-I|--stripesize  StripeSize]]
       {-l|--extents LogicalExtentsNumber[%{VG|PVS|FREE}] |
	-L|--size  LogicalVolumeSize[kKmMgGtT]}  [-M|--persistent y|n] [--minor minor] [-m|--mir-
       rors Mirrors [--nosync] [--mirrorlog  {disk|core}]  [--corelog]	[-R|--regionsize  Mirror-
       LogRegionSize]]	 [-n|--name  LogicalVolumeName]  [-p|--permission  r|rw]  [-r|--readahead
       ReadAheadSectors|auto|none] [-t|--test]	[-v|--verbose]	[-Z|--zero  y|n]  VolumeGroupName
       [PhysicalVolumePath...]

       lvcreate {-l|--extents LogicalExtentsNumber[%{VG|FREE}] |
	-L|--size LogicalVolumeSize[kKmMgGtT]} [-c|--chunksize ChunkSize] -s|--snapshot -n|--name
       SnapshotLogicalVolumeName OriginalLogicalVolumePath

DESCRIPTION
       lvcreate creates a new logical volume in a volume group ( see 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
       vgextend(8)  ) with other physical volumes or by reducing existing logical volumes of this
       volume group in size ( see lvreduce(8) ).
       The second form supports the creation of snapshot logical volumes which keep the  contents
       of the original logical volume for backup purposes.

OPTIONS
       See lvm for common options.

       -c, --chunksize ChunkSize
	      Power of 2 chunk size for the snapshot logical volume between 4k and 512k.

       -C, --contiguous y|n
	      Sets  or resets the contiguous allocation policy for logical volumes. Default is no
	      contiguous allocation based on a next free principle.

       -i, --stripes Stripes
	      Gives the number of stripes.  This is equal to the number of  physical  volumes  to
	      scatter the logical volume.

       -I, --stripesize StripeSize
	      Gives the number of kilobytes for the granularity of the stripes.
	      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.

       -l, --extents LogicalExtentsNumber[%{VG|PVS|FREE}]
	      Gives  the  number of logical extents to allocate for the new logical volume.  This
	      can also be expressed as a percentage of the total space in the Volume  Group  with
	      the  suffix  %VG,  of  the remaining free space in the Volume Group with the suffix
	      %FREE, or of the remaining free space for the specified PhysicalVolume(s) with  the
	      suffix %PVS,

       -L, --size LogicalVolumeSize[kKmMgGtTpPeE]
	      Gives  the  size	to  allocate  for the new logical volume.  A size suffix of K for
	      kilobytes, M for megabytes, G for gigabytes, T for terabytes, P for petabytes or	E
	      for exabytes is optional.
	      Default unit is megabytes.

       --minor minor
	      Set the minor number.

       -M, --persistent y|n
	      Set to y to make the minor number specified persistent.

       -m, --mirrors Mirrors
	      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 poten-
	      tially 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.

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

       -n, --name LogicalVolumeName
	      The name for the new logical volume.
	      Without this option a default names of "lvol#" will be generated where # is the LVM
	      internal number of the logical volume.

       -p, --permission r|rw
	      Set access permissions to read only or read and write.
	      Default is read and write.

       -r, --readahead ReadAheadSectors|auto|none
	      Set read ahead sector count of this logical volume.  For volume groups  with  meta-
	      data  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.

       -R, --regionsize MirrorLogRegionSize
	      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.

       -s, --snapshot
	      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. The snapshot 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 lvextend(8) to grow it.
	      Shrinking a snapshot is supported by lvreduce(8) as well. Run lvdisplay(8)  on  the
	      snapshot in order to check how much data is allocated to it.

       -Z, --zero y|n
	      Controls zeroing of the first KB of data in the new logical volume.
	      Default is yes.
	      Volume will not be zeroed if read only flag is set.
	      Snapshot volumes are zeroed always.

	      Warning: trying to mount an unzeroed logical volume can cause the system to hang.

Examples
       "lvcreate -i 3 -I 8 -L 100M vg00" tries to create 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.

       "lvcreate  -m1  -L  500M vg00" tries to create a mirror logical volume with 2 sides with a
       useable size of 500 MiB.  This operation would require 3 devices  -  two  for  the  mirror
       devices and one for the disk log.

       "lvcreate  -m1 --mirrorlog core -L 500M vg00" tries to create 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".

       "lvcreate --size 100m --snapshot --name snap /dev/vg00/lvol1"
       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.

SEE ALSO
       lvm(8), vgcreate(8), lvremove(8), lvrename(8) lvextend(8), lvreduce(8), lvdisplay(8), lvs-
       can(8)

Sistina Software UK		 LVM TOOLS 2.02.44-cvs (02-17-09)		      LVCREATE(8)


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