[mythtvnz] File System for RAID-5

[James Booth]

On Sunday 21 June 2009 14:26:27 David Zanetti wrote:
> On Thu, 2009-06-18 at 12:57 +1200, James Booth wrote:
> > Thanks Steve. RAID1 with LVM will give me what I need, I was just
> > hoping for RAID 1+0 so I could also get the performance gain, which
> > may be handy if I end up with three frontends all watching and
> > recording HD at the same time.
>
> For read streams, software RAID-1 will scatter the workload over both
> disks. So if you have a few front-ends reading, it won't actually be
> single-disk performance.
>
> Write in *all* RAID modes has a penalty, it's a fair bit lighter in 1
> than 5 purely because 1 involves writing to less disks to update a
> block.
>
> My preferred approach is RAID-1 pairs with LVM spanning the whole set.
> This gives me good reliability without too much loss in performance, and
> an easy migration path to more storage, thanks to various uses of
> degraded array modes.
>
> RAID-5 only makes sense if you are seriously strapped for cash or
> physical space to put disks. Otherwise, the write performance is slower,
> the failure cases are a bit more hairy, and expansion is even hairier.
>
> Go with simple disk systems, people! I've lost enough over the years to
> pushing my luck, and you really want simple arrangements.

Yep, that's just what I've gone for. Splashed for an extra HDD and now have 2 
x RAID-1 with LVM spanning them (non-striped, to make future expansion 
easier). Have gone with XFS, and everything seems good.
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