Re: Kernel 2.6.15.1 + NFS is 4 times slower than FTP!?

From: Justin Piszcz
Date: Tue Jan 17 2006 - 13:37:07 EST


Writing from SRC(A) -> DST(B).
I have not tested reading, but as I recall there were similar speed issues going the other way too, although I have not tested it recently.

Justin.

On Tue, 17 Jan 2006, Trond Myklebust wrote:

On Tue, 2006-01-17 at 13:24 -0500, Justin Piszcz wrote:
Alan, is it normal for FTP to be 2x as fast as NFS?
With 100mbps, I never seemed to have any issues, but with GIGABIT I
definitely see all sorts of weird issues.

Reading or writing?

The readahead algorithm has been borken in 2.6.x for at least the past 6
months. It leads to NFS collapsing down to 4k reads on the wire instead
of doing 32k or 64k.
An effort was made to look at fixing this, but it turns out that nobody
really understands the current messy implementation, and so progress has
been slow.

Cheers,
Trond

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