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Re: NFS performances

On May 12, 2014, at 11:03 AM, Emmanuel Dreyfus wrote:


I have a NFS setup with both NetBSD 6 client and server over a
gigabit network. Theperformance seems week, even whle client,
server and network are almost idle.

The test: time dd if=/dev/zero of=test bs=1024k count=100

Done on the NFS server itself:
   5.31s real 0.00s user 0.39s system

Done over NFS:
   9.82s real 0.00s user 0.12s system

The overhead looks huge. This is a UDP mount with a 1500 bytes MTU,
ping is at 0.8 ms from a virtualized client, ang 0.28 ms for a physical one.

Are the numbers reasonable? Should I consider a 59% NFS overhead  as
acceptable, or are there some parameters to tweak?

Emmanuel Dreyfus

Don't know what to call it, maybe a block-buffer-interleave issue ,
don't know if it is this ... just throwing it out there ...

BUT, what if that's a big block size (or buffer ) that NFS  will
NEVER ever call read with buffers  (or blocks that size)  ???

Are you using a berkley flavor data-dump  that will share with you
when the blocksize is bigger than a buffer dd can pass to read(2) or write(2) ?
by outputting 0+31459  etc.  I believe GNU and also Solaris decided it
(mid '90's) to 'mock-it-up' so the user doesn't get confused...

maybe make the file in /tmp on client once and just 'time cp /tmp/ testfile /nfs/etc/.'
and let the system pick the blocks and buffer sizes naturally.

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