On Sun, Feb 09, 2003 at 05:48:25PM -0600, Dan Nelson wrote:
> In the last episode (Feb 09), Tillman said:
> > Which sysctl is this? The closest I can find is:
> >
> > # sysctl -a | grep nfs | grep sync
> > vfs.nfs.async: 0
>
> Same one. They split the server sysctls out into nfsrv in 5.*.
That makes sense.
> > If that's the one, it may still not be necessary. I'm getting about
> > 8.5-9 Megabytes/s on NFS reads from a Linux 2.4 client (on a 100Mbit
> > switched LAN) with it set to 0, as measured by Bonnie++. This is
> > fairly close to the 12MB/s fast ethernet theoretical maximum, so I'm
> > happy with performance.
>
> It only applies to writes. With it set to 0 (the default), FreeBSD
> follows the NFS spec and does not return from NFSv2 write or NFSv3
> commit calls without having synced the data to disk. This can slow you
> down if you are not on a battery-backed RAID or ramdisk. With NFSv3
> it's not so bad since it supports async client writes (i.e. separate
> write and commit calls).
When I was benchmarking with bonnie++, I found NFSv2 with async writes
turned on to be only marginally faster than v3 with sync'ed commits
(under 10% difference). Given the additional safety, I like using sync
:-)
Thanks for the info,
-T
--
A man may fight the greatest enemy, take the longest journey, survive the most
grievous wound -- and still be helpless in the hands of the woman he loves.
- Zensunni Wisdom from the Wandering
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