Re: 2.2.15 slow NFS

From: Neil Brown (neilb@cse.unsw.edu.au)
Date: Tue Jun 06 2000 - 19:43:42 EST


On Wednesday June 7, jens@pinguin.conetix.de wrote:
> Hi,
>
> please CC: me as I don't read linux-kernel regularly.

Who has the time!!

>
> I'm running Mandrake Linux 7.0 (2.2.14-15mdk) on a NFS client, and Debian
> 2.2 (but with a Mandrake 2.2.15-6mdk kernel) on a NFS server. NFS speed from
> server to client is satisfactory (about 4MB/sec over 100MBit Ethernet). The
> other direction is really, really slow. (100k/sec)

Writing over NFS is usually slower than reading, though a factor of 40
does seem a bit steep.

1/ What flags are you using when exporting. In particular, do you
  include the "sync" flag? You should for safety, but there is a
  speed cost.
  If you are using "sync" try using "async" and do the same tests.
  That might help isolate where the slowness is.

2/ What size files are you writing to? If there are big enough to
  have double-indirect blocks, and you are using "sync", then the
  implementation of fsync in 2.2 hits you REALLY HARD.
  Compare writing to large and small files with and without sync, and
  let me know what you get.

NeilBrown

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