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 lvm(7)								      lvm(7)




 NAME
      lvm - Logical Volume Manager (LVM)

 DESCRIPTION
      The Logical Volume Manager (LVM) is a subsystem for managing disk
      space.  The HP LVM subsystem offers value-added features, such as
      mirroring (with the optional HP MirrorDisk/UX software), high
      availability (with the optional HP ServiceGuard software), and
      striping, that enhance availability and performance.

      Unlike earlier arrangements where disks were divided into fixed-sized
      sections, LVM allows the user to consider the disks, also known as
      physical volumes, as a pool (or volume) of data storage, consisting of
      equal-sized extents.  The default size of an extent is 4 MB.

      An LVM system consists of arbitrary groupings of physical volumes,
      organized into volume groups.  A volume group can consist of one or
      more physical volumes.  There can be more than one volume group in the
      system.  Once created, the volume group, and not the disk, is the
      basic unit of data storage.  Thus, whereas earlier one would move
      disks from one system to another, with LVM, one would move a volume
      group from one system to another.	 For this reason it is often
      convenient to have multiple volume groups on a system.

      Volume groups can be subdivided into virtual disks, called logical
      volumes.	A logical volume can span a number of physical volumes or
      represent only a portion of one physical volume.	The pool of disk
      space that is represented by a volume group can be apportioned into
      logical volumes of various sizes.	 The size of a logical volume is
      determined by its number of extents.  Once created, logical volumes
      can be treated just like disk partitions.	 Logical volumes can be
      assigned to file systems, used as swap or dump devices, or used for
      raw access.

    Commands
      LVM information can be created, displayed, and manipulated with the
      following commands:

	   lvchange	     Change logical volume characteristics
	   lvcreate	     Stripe, create logical volume in volume group
	   lvdisplay	     Display information about logical volumes
	   lvextend	     Increase space, increase mirrors for logical
			     volume
	   lvlnboot	     Prepare logical volume to be root, primary
			     swap, or dump volume
	   lvmmigrate	     Prepare root file system for migration from
			     partitions to logical volumes
	   lvreduce	     Decrease number of physical extents allocated
			     to logical volume
	   lvremove	     Remove one or more logical volumes from volume
			     group



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 lvm(7)								      lvm(7)




	   lvrmboot	     Remove logical volume link to root, primary
			     swap, or dump volume
	   pvchange	     Change characteristics of physical volume in
			     volume group
	   pvcreate	     Create physical volume for use in volume group
	   pvdisplay	     Display information about physical volumes
			     within volume group
	   pvmove	     Move allocated physical extents from one
			     physical volume to other physical volumes
	   vgcfgbackup	     Create or update volume group configuration
			     backup file
	   vgcfgrestore	     Display or restore volume group configuration
			     from backup file
	   vgchange	     Set volume group availability
	   vgcreate	     Create volume group
	   vgdisplay	     Display information about volume groups
	   vgexport	     Export an volume group and its associated
			     logical volumes
	   vgextend	     Extend an volume group by adding physical
			     volumes
	   vgimport	     Import an volume group onto the system
	   vgreduce	     Remove physical volumes from an volume group
	   vgremove	     Remove volume group definition from the system
	   vgscan	     Scan physical volumes for volume groups

      The following commands are also available if the HP MirrorDisk/UX
      software is installed:

	   lvmerge	  Merge two logical volumes into one logical volume
	   lvsplit	  Split mirrored logical volume into two logical
			  volumes
	   lvsync	  Synchronize stale mirrors in logical volumes
	   vgsync	  Synchronize stale logical volume mirrors in volume
			  groups

 EXAMPLES
      The basic steps to take to begin using LVM are as follows:

	   +	Identify the disks to be used for LVM.

	   +	Create an LVM data structure on each identified disk (see
		pvcreate(1M)).

	   +	Collect all the physical volumes to form a new volume group
		(see vgcreate(1M)).

	   +	Create logical volumes from the space in the volume group
		(see lvcreate(1M)).

	   +	Use each logical volume as if it were a disk section (create
		a file system, or use for raw access).



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 lvm(7)								      lvm(7)




      To configure disk /dev/dsk/c0t0d0 as part of a new volume group named
      vg01.

	   First, initialize the disk for LVM with the pvcreate command.

		pvcreate /dev/rdsk/c0t0d0

	   Then, create the pseudo device file that is used by the LVM
	   subsystem.

		mkdir /dev/vg01
		mknod /dev/vg01/group c 64 0x030000

	   The minor number for the group file should be unique among all
	   the volume groups on the system.  It has the format 0xNN0000,
	   where NN ranges from 00 to 09.  The maximum value of NN is
	   controlled by the kernel tunable parameter, maxvgs.

	   Create the volume group, vg01, containing the physical volume,
	   /dev/dsk/c0t0d0, with the vgcreate command.

		vgcreate /dev/vg01 /dev/dsk/c0t0d0

	   You can view information about the newly created volume group
	   with the vgdisplay command.

		vgdisplay -v /dev/vg01

	   Create a logical volume of size 100 MB, named usrvol, on this
	   volume group with the lvcreate command.

		lvcreate -L 100 -n usrvol /dev/vg01

	   This creates two device files for the logical volume,
	   /dev/vg01/usrvol, which is the block device file, and
	   /dev/vg01/rusrvol, which is the character (raw) device file.

	   You can view information about the newly created logical volume
	   with the lvdisplay command.

		lvdisplay /dev/vg01/lvol1

	   Any operation allowed on a disk partition is allowed on the
	   logical volume.  Thus, you can use usrvol to hold a file system.

		newfs /dev/vg01/rusrvol hp7937
		mount /dev/vg01/usrvol /usr

 SEE ALSO
      lvchange(1M), lvcreate(1M), lvdisplay(1M), lvextend(1M), lvlnboot(1M),
      lvreduce(1M), lvremove(1M), lvrmboot(1M), pvchange(1M), pvcreate(1M),



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 lvm(7)								      lvm(7)




      pvdisplay(1M), pvmove(1M), vgcfgbackup(1M), vgcfgrestore(1M),
      vgchange(1M), vgcreate(1M), vgdisplay(1M), vgexport(1M), vgextend(1M),
      vgimport(1M), vgreduce(1M), vgremove(1M), vgscan(1M).

      Managing Systems and Workgroups.

      If HP MirrorDisk/UX is installed: lvmerge(1M), lvsplit(1M),
      lvsync(1M), vgsync(1M).

      If HP ServiceGuard is installed: cmcheckconf(1M), cmquerycl(1M),
      Managing MC/ServiceGuard.











































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