raid10n2/xfs setup guidance on write-cache/barrier

[keld at keldix.com]

On Thu, Mar 15, 2012 at 02:07:25PM +0000, Peter Grandi wrote:
> >>> I want to create a raid10,n2 using 3 1TB SATA drives.
> >>> I want to create an xfs filesystem on top of it. The
> >>> filesystem will be used as NFS/Samba storage.
> 
> Consider also an 'o2' layout (it is probably the same thing for a
> 3 drive RAID10) or even a RAID5, as 3 drives and this usage seems
> one of the few cases where RAID5 may be plausible.

Well, for a file server like NFS/Samba, you could also consider raid10,f2.
I would think you could get about double the read performance compared to n2 and o2
layouts, and also for individual read transfers on a running system
you would get somthing like double the read performance. 
Write performance could be somewhat slower (0 to 10 %) bot as users
are not waiting for writes to complete, they will probably not notice.
 
best regards
keld