[mythtvnz] File System for RAID-5

[Jim Cheetham]

On Mon, Jun 15, 2009 at 2:30 PM, <james at booths.net.nz> wrote:
> Having just had a near-death experience with my non-RAID LVM system
> for Myth, I am about to convert everything to a RAID-5 setup (software
> RAID) with LVM on top.

Even though it's been said before on this thread, I'll say it again ...

Don't use RAID-5. The failure modes you get in RAID-5 coupled with the
disk health information available to the OS (i.e. basically none) mean
that you stand a reasonable chance of losing all your data
unexpectedly. RAID5 is a disk storage model based on a different
economic value for disks/controllers to how we operate today. Don't
use it :-)

You are storing archive data, so you don't need write performance,
just read performance. RAID1 is your simplest friend. Simplicity means
it's quick to recover when things go wrong. And they will :-)

You can have multiple disks in your RAID1 for redundancy, three would
be plenty. Two is probably acceptable, given the delivery times for
new disks these days. LVM on top gives the flexibility for growing &
importing volumes, but you know that.

> Before I go ahead does anyone have any
> recommendations on best choice of file system to use, given that it
> will be within LVM on RAID-5? I was going to go with XFS, but that
> cannot be shrunk, which (as I have found) can be very irritating when
> trying to reorganise your disks in an LVM.

Why shrink a filesystem? I guess if you haven't figured out how you
want to store things, perhaps ... but in general, filesystems only
grow :-)

Just stick with ext3 unless you really know the details of why you're
using something else (yes, not very sexy is it?). XFS should be good
by default for large objects, but you already don't like that ...

-jim