From: "Talpey, Thomas" <Thomas.Talpey@netapp.com>
Subject: Re: nfs performance problem
Date: Fri, 26 Oct 2007 13:01:37 -0400
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	<7B68ECC3-7EBA-442F-9FFD-A0E3F2DCC61A@oracle.com>
	<20071025193457.GE4499@jakobus.spotify.net>
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Cc: nfs@lists.sourceforge.net
To: Andreas Schuldei <andreas@schuldei.org>
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At 03:34 PM 10/25/2007, Andreas Schuldei wrote:
>> But don't expect to get better data throughput over NFS than you see 
>on your local NFS server. 
>
>That is exactly the point. on my server i get 4*50Mbytes =
>200Mbyte/s out of the disks (with the above FOR loop around the
>find and dd) and when i export on the same server the disks to an
>nfs client i all of a sudden loose ~75% of the performance.

Andreas - you mentioned earlier in the thread that you're using 2.6.22
as the server kernel. You might consider moving it forward to 2.6.23,
as there is a significant readahead improvement/fix there. When you
run a local read, all readahead is perfect. However on older kernels
serving NFS, the reordering of reads due to Linux's multithreaded nfsd's
triggers several issues which spook the readahead into truly awful
behavior.

Fengguang Wu's changes are merged in 2.6.23, in testing with NFS/RDMA
we now see the same performance over the wire as locally, for any
number of readers.

My one caveat to this is that your files are relatively small, so I would
not expect a truly dramatic speedup from it. It's certainly worth trying,
there are other improvements in 2.6.23.

Do you have Infiniband or iWARP adapters in your environment? If you're
worried about bandwidth and application startup latency, using it could
certainly help. You'd need to run a 2.6.24-rc1 client though, and some
assembly is still required to use the server (it's not yet upstream).

Tom.

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