[CentOS] RAID5 or RAID50 for database?

Thu May 22 17:16:44 UTC 2008
Warren Young <warren at etr-usa.com>

Rudi Ahlers wrote:
> So, how does it perform with 6 discs for example? Say I have 3 HDD's in 
> RAID-0, and another 3 in RAID-0, then RAID-1 the 2 RAID-0 stripes. 

There's actually two kinds of RAID-10.  Some like to say RAID-01 or 
RAID-1+0 or things like that to distinguish them.  It's a matter of 
whether it's mirrors over stripes or stripes over mirrors.  You're 
talking about mirrors over stripes, but I'm talking about doing it the 
other way around.

Your way has the advantage of letting you add disks in pairs, but to get 
that you get only single-disk redundancy: if a second disk goes out, 
your array is gone, no matter which disk it is.

If you do it the other way, you have to use groups of 4 (two mirrors 
striped together) but you get the advantage that with a single disk 
missing, you can lose another if it's in the other mirror.  Of course, 
if you lose two in the same mirror, you're toast.

> And what would you recommend on 8 / 10 HDD's?

As I said, usually RAID-5 or -6 usually makes more sense with so many 
spindles.  If you're talking RAID-10 (my way) with so many disks, it 
starts getting expensive with 8, 12, etc.