[nSLUG] Best way to upgrade mirrored disks to larger capacity?

D G Teed donald.teed at gmail.com
Wed May 11 09:16:27 ADT 2011

I'm coming up on a couple of systems running mirrored software RAID
where I'd like to swap out smaller disks for a pair of 1 TB disks.
In both cases there is 200GB or more of disk used, and the
partitions include / root partition.

There are SATA connectors for only 2 drives on the mainboard
and they are not hot swappable.

Of course it would be nice to minimize downtime.

I can think of a couple of ways of upgrading the disks while attempting
to keep things running as much as possible.

One method is:

- degrade the mirrors by removing one disk from the RAID configuration (fail
then remove)
- power down and swap the disk removed from the mirror with a higher
- boot from old disk and set up new, "missing disk" RAID partitions on new
- boot from rescue CDROM disk and copy partitions from old to new
- install grub on new disk
- power down and add second new disk, boot from first new disk
- set up partitions on second new disk, add into array
- install grub on second new disk

Another approach would be similar, but to clone (dd) the old partitions to
and grow the file system (mdadm --grow /  resize2fs) on the higher capacity.

There might be other approaches these days.
If this is the last growth in the life of the system,
I don't see the value of getting into LVM.  It is also
a bit tricky to find guides on LVM which are up to
date for LVM2.  What are hints to indicate an article
isn't talking about LVM2?

If anyone has an alternate approach or anything they have learned to
help keep the downtime to a minimum, I'd like to hear.

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