Thursday, January 7, 2010

Hot Migrate Root Volumes in AIX

AIX is one of the few OSes that, out of the 'box', can replace boot disks while the OS is running without an outage.  Of course, the standard disclaimers apply... namely, test this on a non-production LPAR and make sure you have backups.  This is extremely helpful for storage array migrations (bringing an LPAR under a SVC, for example) and general maintenance.

If you’re running under VIO Servers, it even allows complete cleanup to occur online.  I recommend a reboot at the end to be safe, but it really isn't necessary.

Assumptions:  All the target disks are currently configured on the LPAR and are not in any volume groups.

Step 0: MAKE SURE TO HAVE A CURRENT MKSYSB AND BACKUP.

Step 1: Replace an old root hdisk with the new one. If this fails due to the destination disk being smaller, go to the alternate instructions below
$ replacepv OLDDISK1 NEWDISK1
0516-1011 replacepv: Logical volume hd5 is labeled as a boot logical volume.
0516-1232 replacepv:
NOTE: If this program is terminated before the completion due to
a system crash or ctrl-C, and you want to continue afterwards
execute the following command
replacepv -R /tmp/replacepv385038
0516-1011 replacepv: Logical volume hd5 is labeled as a boot logical
volume.
Step 2: Verify that the old disk is not defined to any volumegroups:
$ lspv
OLDDISK1 00007690a14xxxxx None
NEWDISK1 00007690a14xxxxx rootvg  active
OLDDISK2 00007690913xxxxx rootvg  active
Step 3: Add the boot image to the new disk:
$ bosboot -ad NEWDISK1
bosboot: Boot image is 30441 512 byte blocks.
Step 4: Repeat steps 1-3 for the second root disk (if replacing both
root disks)

Step 5: Adjust the bootlist
$ bootlist -om normal  NEWDISK1 NEWDISK2
$ bootlist -om service NEWDISK1 NEWDISK2
Step 6: Remove the old hdisks.
$ rmdev -dl OLDHDISK
Step 7: Remove the old disk mappings from the VIO Server if applicable.
$ rmdev -dev OLDMAPPING
Step 9: Run savebase
$ savebase
Alternate Instructions

Step A1: Place the replacement hdisks into the volumegroup:
extendvg rootvg NEWDISK
Step A2: Migrate the disks (you must have PPs sufficient to migrate the
disk):
migratepv OLDDISK NEWDISK
Step A3: Validate that there is no data on the old disk
lspv -l OLDDISK
Step A4: Remove the OLDDISK from the Volumegroup
reducevg rootvg OLDDISK
Step A5: Add the boot image to the new disk:
$ bosboot -ad NEWDISK1
Step A6: Repeat steps A1-A5 for the second root disk.

Step A7: Continue with step 5 above (namely, adjust the bootlist, cleanup left over disks, and savebase).

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