NFS performance (can't use "async")

[NoOp]

On 07/19/2012 03:10 AM, Wipe_Out wrote:
> Hi,
> 
> Recently I have been testing various options to create a NFS server for
> storing virtual machine disk images.. For data integrity sake running as
> "async" is not an option and this appears to be the most commonly
> recommended "improvement"..
> 
> The issue I have is not so much with raw throughput, I have been able to
> saturate a 1GbE connections easily.. The issue is more to do with write
> operations.. On FreeBSD+ZFS I can get about 800 FSYNCS/s.. On Ubuntu 12.04
> (tested with ext3/ext4/XFS/BtrFS) I can only get 15-20.. This is on the
> exact same hardware..
> 
> I don't think its file system related because of all the file systems ZFS
> and BtrFS should have the biggest overhead but switching from ext4 to BtrFS
> didn't change the performance results..
> 
> I haven't yet tried other distro's to see if the slow NFS is Ubuntu related
> but I can't see why is would be..
> 
> Does anyone have any ideas why there is such a huge difference between the
> performance of the FreeBSD and Ubuntu NFS servers?

<https://launchpad.net/+search?field.text=nfs+performance&x=0&y=0>

Perhaps you are running into these bugs?
<https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1006446>
[nfs4 causes enormous load in ubuntu-server making it unusable]
<quote>
SLOWNESS:
That is the thing. The ubuntu nfs server is actually NOT slow at all.
During my dd tests, it wrote half a gigabyte per second to its iscsi
backends. It's _throughput_ is better than that of the redhat server.
As far as I can tell, it falls down because it makes client side
processes that want to do IO wait on other writes. A simple 'ls' has to
wait until a write has been completed. And both server and client used
async nfs. People's firefoxes freeze all the time because firefox need
to read and write a lot to its cache and other files in the .mozilla
directory.
The dovecot imap server almost grinds to a halt trying to write all
those little files in people's /home/$USER/Maildir's.
The problems go on and on. Basically, a complete network of workstations
is almost unusable because of this.
Upfront tests were done of course, but showed only the excellent
throughput but not the appalling `waiting´ behaviour.
With redhat 6 there is no such problem.
</quote>

That bug was been marked as a duplicate of:
<https://bugs.launchpad.net/ubuntu/+source/nfs-utils/+bug/879334>
[nfsd from nfs-kernel-server very slow and system load from 25%-100%
from nfsd]