Tuesday, July 21, 2009

vgimport with persistent DSFs

When upgrading a server from 11.23 to 11.31 using a cold-install, the procedure to migrate your VGs and filesystems boils down to this:
  1. vgexport -s -p -m vg_name.map vg_name
  2. Keep a backup copy of the fstab
  3. Reinstall
  4. vgimport -N -s -m vg_name.map vg_name
  5. Put back the filesystems in fstab, create the directories and mount

Pretty straightforward, huh?

System administrators familiar with vgexport/vgimport will notice the new -N option which, according to the man page does this:

-N Configure the volume group by populating
persistent device special files in the /etc/lvmtab
or /etc/lvmtab_p file, corresponding to the volume
group, vg_name. (See intro(7) for information
about device special files.) This option can only
be used with -s option. If vgimport is invoked
without a -N option, legacy device special files
will be used to populate the /etc/lvmtab or
/etc/lvmtab_p file.

This option may become obsolete in future

What this option does, is importing your imported VGs with persisten DSFs. If you don't do this, they will be imported using the legacy DSFs, and if you're on a SAN this means that PVLinks will still be used. I think that the storage stack on 11.31 is smart enough to apply multipathing in the background to legacy DSFs but it's much cleaner to use the persistent DSFs right away.

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