A couple things to check, Brian...
1) How large is your RAID-Z2 pool (# of spindles)? If it's rather
large (say, above 8), you might be running into problems from that.
2) Check to see if your fileserver process is fully resident in
memory (not swapped out.) ZFS's ARC can get VERY greedy and end up
pushing out real stuff to swap. If you've got a callback table size
on your fileserver, there will be quite a few chunks of memory that
it uses which may look like good candidates for swapping-out because
they don't get accessed much -- but when they do, it'll drag your
fileserver to a crawl for the time when its got to swap them in. If
this is the case, figure out how much ram you can dedicate to the
ARC, and pin its maximum size. (see: http://www.solarisinternals.com/
wiki/index.php/
ZFS_Best_Practices_Guide#Memory_and_Dynamic_Reconfiguration_Recommendati
ons )
-rob
On Jul 11, 2007, at 16:49, Brian Sebby wrote:
Hello,
I've been getting intermittant reports of slow read performance on
a new
AFS file server that I recently set up based on ZFS. It is using
locally
attached disks in a RAID-Z2 (double parity) configuration. I was
wondering
if anyone might be able to provide any ideas for tuning /
investigating
the problem. The slow performance that's been reported seems to be
against
a RW volume with no replicas.
Right now, I am using OpenAFS 1.4.4 with the "no fsync" patch. The
options I'm using for the fileserver are "-nojumbo" and "-nofsync".
I've also set the ZFS parameters "atime" to "off" and "recordsize"
to "64K" as recommended in Dale Ghent's presentation at the OpenAFS
workshop.
There are a bunch of file server options that I'm not sure if they
would
help or not. Any advice would be appreciated as I'm looking at ZFS-
based
file servers for some new file servers I'm setting up, but my
experience
so far has been mostly with the OpenAFS 1.2 inode-based file server.
Brian
--
Brian Sebby ([EMAIL PROTECTED]) | Unix and Operation Services
Phone: +1 630.252.9935 | Computing and Information Systems
Fax: +1 630.252.4601 | Argonne National Laboratory
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