Re: [RFC] nfs: use 4*rsize readahead size

From: Trond Myklebust
Date: Tue Mar 02 2010 - 09:19:44 EST

On Tue, 2010-03-02 at 11:10 +0800, Wu Fengguang wrote:
> Dave,
> Here is one more test on a big ext4 disk file:
> 16k 39.7 MB/s
> 32k 54.3 MB/s
> 64k 63.6 MB/s
> 128k 72.6 MB/s
> 256k 71.7 MB/s
> rsize ==> 512k 71.7 MB/s
> 1024k 72.2 MB/s
> 2048k 71.0 MB/s
> 4096k 73.0 MB/s
> 8192k 74.3 MB/s
> 16384k 74.5 MB/s
> It shows that >=128k client side readahead is enough for single disk
> case :) As for RAID configurations, I guess big server side readahead
> should be enough.

There are lots of people who would like to use NFS on their company WAN,
where you typically have high bandwidths (up to 10GigE), but often a
high latency too (due to geographical dispersion).
My ping latency from here to a typical server in NetApp's Bangalore
office is ~ 312ms. I read your test results with 10ms delays, but have
you tested with higher than that?

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