16-disk SW RAID-6 on RHEL?

[Ray Van Dolson]

On Tue, Aug 10, 2010 at 07:33:47AM -0700, Peter Ruprecht wrote:
> Hi everyone,
> 
> I could use a little advice.  I'm considering setting up a 16-disk 
> software RAID-6 system for use as a samba fileserver.  The disks would 
> be 2TB SATA in an external enclosure attached via SAS to the server 
> (RHEL5, 2x Xeon E5420 processors with 4 cores, 16 GB RAM).
> 
> I have done software RAID-5 with 6 disks and gotten satisfactory 
> performance, but has anyone else tried SW RAID on a bigger scale?  Would 
> that just be nuts?
> 
> So why not just buy a HW RAID system?  Well, in this case cost is a big 
> issue.  Also, in the past I've had some issues with RAID controllers 
> freaking out leaving all the data inaccessible, which I think is less 
> likely with SW RAID.
> 
> Finally, is there a reasonable RH-compatible alternative to xfs for a 
> 16TB+ filesystem?  Or is xfs now less iffy than it was a few years ago?

I don't like going over 10 disks or so in a RAID-set, but maybe I'm old
school.  You definitely would want to do RAID-6 with that many... these
days processors are plenty beefy enough to handle parity calculations
with that many spindles, but keep in mind your rebuild times are going
to be pretty long .. 14 disks to completely read...

I think I'd go with two 8 disks RAID-6 arrays (and definitely have a
spare ready), but I could be on the conservative side. :)

Ray