xfs on lvm with dm-thin and multipath/multi-volume

[Dave Hall <kdhall@xxxxxxxxxxxxxx>]

Stan,

It's been a while.  I have some new hardware and a chance to do a good 
XFS layout rather than wonder why previous bad layouts don't perform.
My hardware is a well appointed server with dual HBAs a large 
SAS-attached array with dual controllers.  I'd like to partition 22 
spindles (1.8TB each) into multiple small volumes (RAID 5 - 4+1 or RAID 
6 - 8+2) with some hot spares and access via multipath. The PVs would be 
striped or concatenated together with LVM.
I'm wondering about performance with XFS on a dm-thin logical volume and 
thin snapshots.  I'm also concerned about XFS layout in general - RAID 
stripe alignment and the appropriate number of allocation groups, and if 
this would be done differently with thin volumes.
The workload is NFS with a very random access pattern and higher than 
average write activity.
Would you be willing to comment on the current 'state of the art' for 
all of this?  Are there any tools or guidelines for optimal XFS layout?
Thanks.

-Dave

Dave Hall
Binghamton University
kdhall@xxxxxxxxxxxxxx
607-760-2328 (Cell)
607-777-4641 (Office)