[geeks] RAID0+1 and ideas, etc...

[Jonathan Katz]

A few things...

The app we're using (current rev) requires XFS as the filesystem (the
next rev, which was just released and is a little too bleeding edge
for us does not.) It does not really scale across multiple servers,
and a redundant/HA-type server setup isn't in the budget; we gots what
we gots.

There are six total IOFusion Duo cards; each card presents two 1TB
drives. So we have 12 raw drives and 6TB usable. We've had FusionIO
techs involved, and they're good with the mirroring. ( Of course they
are; they get to sell more cards that way! :D ) The FusionIO website
even talks about mirroring practices, but I've seen other blogs where
admins/end users say not to mirror.

I was choosing going with LVM as the primary (and only) volume manager
for this for a few reasons, but the main one is that there seems to be
better support information available. I know in the past that LVM
wasn't happy with RAID 1+0 but that has since changed; I'm actually
using LVM RAID 1 to mirror two FusionIO cards at another customer. As
long as you have a mirror log device set, it works fine. The other
issue is that right now they have two methods of managing the storage
since they're using both the LVM and 'md' facilities and moving to
just one facility makes more sense.