[OpenAFS] Poor performance on new ZFS-based file server

[Robert Banz]

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  (sebby@anl.gov)  |  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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