NFS - slow
rmacklem at uoguelph.ca
Mon Apr 30 11:58:08 UTC 2012
Wojciech Puchar wrote:
> > the server is required to do that. (ie. Make sure the data is stored
> > on
> > stable storage, so it can't be lost if the server crashes/reboots.)
> > Expensive NFS servers can use non-volatile RAM to speed this up, but
> > a generic
> > FreeBSD box can't do that.
> > Some clients (I believe ESXi is one of these) requests FILE_SYNC all
> > the
> > time, but all clients will do so sooner or later.
> > If you are exporting ZFS volumes and don't mind violating the NFS
> > RFCs
> > and risking data loss, there is a ZFS option that helps. I don't use
> > ZFS, but I think the option is (sync=disabled) or something like
> > that.
> > (ZFS folks can help out, if you want that.) Even using
> > vfs.nfsrv.async=1
> > breaks the above.
> thank you for answering. i don't use or plan to use ZFS. and i am
> aware of
> this NFS "feature" but i don't understand - even with syncs disabled,
> writes are not clustered. i always see 32kB writes in systat
The old (default on NFSv3) server sets the maximum wsize to 32K. The
new (default on 9) sets it to MAXBSIZE, which is currently 64K, but
I would like to get that increased. (A quick test suggested that the
kernel works when MAXBSIZE is set to 128K, but I haven't done much
> when running unfsd from ports it doesn't have that problem and works
> FASTER than kernel nfs.
But you had taken out fsync() calls, which breaks the protocol, as above.
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