On Wed, Oct 06, 2010 at 02:03:21PM -0700, Eff Norwood wrote:
> I have a 24 x 1TB system being used as an NFS file server. Seagate SAS disks
> connected via an LSI 9211-8i SAS controller, disk layout 2 x 11 disk RAIDZ2 +
> 2 spares. I am using 2 x DDR Drive X1s as the ZIL. When we write anything to
> it, the writes are always very bursty like this:
> 
> ool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0    232      0  29.0M
> xpool        488K  20.0T      0    101      0  12.7M
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0     50      0  6.37M
> xpool        488K  20.0T      0    477      0  59.7M
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool        488K  20.0T      0      0      0      0
> xpool       74.7M  20.0T      0    702      0  76.2M
> xpool       74.7M  20.0T      0    577      0  72.2M
> xpool       74.7M  20.0T      0    110      0  13.9M
> xpool       74.7M  20.0T      0      0      0      0
> xpool       74.7M  20.0T      0      0      0      0
> xpool       74.7M  20.0T      0      0      0      0
> xpool       74.7M  20.0T      0      0      0      0
> 
> Whenever you see 0 the write is just hanging. What I would like to see is at
> least some writing happening every second. What can I look at for this issue?

First, try to snoop the communication between the NFS server and the NFS
client. Then you'll see whether the "bursting" comes from the client or from
the server.

Then you can do some dtrace magic at either NFS server or NFS client to see
where exactly the problem is.


HTH.

-- 
Marcel Telka
RPE, Systems
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