Logical Volume Manager (lvm) Commands for aix




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Logical Volume Manager (LVM) Commands for AIX







Glossary


Term

Definition

Journaled File System (JFS)

File system that uses a journaled log for faster, more reliable data recovery

Logical Partition (LP)

The LV is made up of LPs.  The LP corresponds to 1 or more (in the case of mirroring) PPs.

Logical Volume (LV)

The VG is subdivided into logical volumes and each LV can have  a file system on it.

Physical Partition (PP)

All physical volumes are subdivided into pps.  PPs are all the same size.

Physical Volume (PV)

Disk that is being managed by LVM.

Rootvg

Default volume group created during installation.  The vg holds the OS filesystems ( /,/usr, /home, /proc /opt,  /tmp,  /var and swap space )

Volume Group (VG)

Area of storage that consists of one or more PVs


Command Summary


Command

Definition

chfs -a size=<#512 byte blocks>

Increases the size of a journaled file system to the total number of  512 byte blocks specified

chfs -a size=<+512 byte blocks>

Increases the size of a journaled file system by the addional number of 512 byte blocks specified.  For example "chfs -a size=+393216 /usr"

chlv -n

Change the name of a logical volume (it must be inactive)

crfs -v jfs -m -g -a size=<# of 512 byte blocks>

crfs -v jfs -m -d  



This command makes a logical volume, mount point with a journaled file system:

creates a jfs file system on a logical volume



df -k

Shows the disk usage of logical volumes on the server.

exportvg  

removes a volume group from a machine

extendvg


Adds a new physical volume to an existing volume group

importvg -y
 

add a volume group to another machine

lslv [-l, m]

Lists information about the logical volumes.  The -l option lists the disks in the logical volume.

lspv
[-l, M, p]

Lists the disks on the server, including the physical volume will give details about that disk.  The -l option will list the details of how the filesystems are distributed on the disk.

lsvg [-l]

Lists the volume groups on the server, including the volume group name will give details about that vg. The -l option will list the logical volumes in the volume group.

lsvpcfg

Lists each vpath and the hdisks that make up the vpath

mklv -y

Makes a logical volume in a volume group

mksysb -l -f  

makes a bootable backup of rootvg

mkvg -y
  . . .


Makes a volume group out of one or more physical volumes

mount   or
mount   if it is already in /etc/filesystems

Mounts the file system for use.

reducevg


Removes a physical volume from a volume group

rmfs  

removes a file system and it's logical volume

rmlv

Removes a logical volume (it must be inactive)

savevg -l -f  

makes a backup copy of another volume group

umount  dismount the file system

Unmounts the filesystem.


Sample LVM Procedures:

Filesystem Procedures


Procedure to create a filesystem using JFS:

  • See below the procedure for creating a logical volume and a filesystem using JFS:


Procedure to extend the size of filesystem using JFS:

  1. "df" to see the filesystem, it's current size, % utilization and the name of it's logical volume

  2. "lslv " to show information about the logical volume including it's volume group name.

  3. "lsvg " to show information about the volume group, including number of free pp's and the pp size

  4. If there are not enough free pp's then see below for procedure to add a disk to a volume group.

  5. "chfs -a size= +4194304 " to grow the filesystem by 2 GB (4194304=2*1024*1024*1024/512)

    • NOTE:  Growing the file system will automatically grow the logical volume

  6. df" shows the file system's current size is 2 GB more than before.

Troubleshooting extending the size of a filesystem using JFS:

  • Error Message:  0516-787 extendlv: Maximum allocation for logical volume is 512.

    • Maximum number of LPs for the logical volume has been exceeded - must increase the allocation

    • Calculate the number of LPs needed = LV Size in MB / LP size in MB

    • chlv -x

Procedure to remove a file system

  1. Unmount the filesystem

  2. Remove the logical volume "rmlv "

  3. Remove the filesystem information from /etc/filesystems

Procedure to reduce the size of a file system - shareold is 8mb and needs to be reduced to 4mb

  1. Create the file system

    1. crfs -v jfs -m /usr/sharenew -g rootvg -a size=8192

    2. this makes a logical volume in the root volume group of 4MB that uses jfs

  2. Mount the volume

    1. mount /usr/sharenew

  3. Move the files from the old file system (/usr/shareold)

    1. cd /usr/shareold

    2. tar cf - | (cd /usr/sharenew; tar xvf -)

    3. cd

  4. Unmount the file systems

    1. umount /usr/sharenew

    2. umount /usr/shareold

  5. Remove the old file system and it's logical volume

    1. rmfs /usr/shareold

  6.   

    1. chfs -m /usr/shareold /usr/sharenew

  7. Mount the new filesystem

    1. mount /usr/shareold

  8. Delete the temporary mount point

    1. rmdir /usr/share



Logical Volume Procedures


Procedure to create a logical volume and filesystem in a volume group using JFS:

  1. lsvg to determine the size of the PP

  2. lslv in similar logical volumes to determine if mirroring is in effect

  3. Calculate the number of PPs needed for the logical volume

    1. bc

    2. scale=2

    3. /

    4. quit

  4. mklv -y  "" <# of LPS>  --> creates the logical volume

  5. crfs -v jfs -d -m / -A yes   --> makes the filesystem, creates the mountpoint and puts it in /etc/filesystems

  6. mount /  --> mounts the new fileystem

  7. df /  --> verifies the mount and the size of the new filesystem

  8. Check the ownership and permissions of the new mount point

    • ls -ld

    • chown owner:group

    • chmod XXX

  1. If mirroring is in effect, then mirror this logical volume to another disk (original and 1 mirror):

    • mklvcopy -s y 2


Check to see if  all of the logical volumes in a volume group are mirrored

  • lsvg -l


Mirror a logical volume after the fact

  •  mklvcopy -s y 2


Volume Group Procedures


Procedure to create a volume group:

  1. lsdev -C -c disk  -> lists available disks (and the hdisk#) on the server

  2. mkvg -y "" hdisk#  --> creates the volume group on the named hard disk

  3. varyonvg   --> activates the volume group

Procedure to add a disk to a volume group (extend the volume group)

  • extendvg

    • Verify the disk has been successfully added to the vg

  • lsvg -p


Procedure to mirror the rootvg:

  1. lspv  --> determine the hdisk#

  2. extendvg rootvg hdisk  --> add the hdisk to the volume group

  3. lspv  -->  verify that the hdisk has been successfully added to the volume group

  4. chvg -Q 'n' rootvg  -->  change the quorum so that the vg will stay active if one of the mirrors fail

  5. mirrorvg -S -c 2 rootvg  --> mirror all of the logical volumes in the volume group

  6. lsvg -l rootvg  --> verify successful mirroring (pps will appear "stale" until synchronization is complete).

  7. bosboot -a  -->  update the boot image information

  8. bootlist -m normal -o hdisk0 hdisk1  --> create a new bootlist

  9. bootlist -m normal -o  --> verify the bootlist is correct

Procedure to increase the number of LP's available
Assume we receive an error that the maximum number of LP's had been exceeded, and the maximum number of LP's defined was 1100:

  1. "lsvg " to show the total PP's available in the volume group =1250

  2. "lsvg -l " to show the total PP's used in all logical volumes in that volume group (showed sys1log, the jfs log was using 2 PP's)

  3. "chlv -x 1248 " to change the maximum number of LP's from 1100 to 1248 (1250 PP's in the volume group - 2 PP's used by the jfs log  = 1248 available)


Physical Disk Procedures


Procedure to find disks/vpaths that are unallocated

  • lsvpcfg

    • This will show disks/vpaths and the volume group they are allocated to

  • lspv|grep None

    • This will show pvs and whether they are asssociated with a volume group

    • Note:  For vpaths, the hdisks will show as none, but they may be allocated to a vpath - you must grep each hdisk with the lsvpcfg


Procedure to make a new lun available to AIX

  • Allocate the new lun on the SAN

  • Run "cfgmgr"

  • Verify the new vpatch/hdisk by running "lsvpcfg"

    • There should be a new vpath and it should be available with no volume group - if not, rerun cfgmgr


Procedure to list the PVs in a volume group:

  • lsvg -p


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