[mythtv-users] [OT]Slow JFS writes over NFS

[Cool Frood]

On Thu, Jan 28, 2010 at 3:23 PM, John Finlay <finlay at moeraki.com> wrote:
> For historical reasons I have 3 mythtv disks that use JFS and 1 that use
> XFS. I recently discovered that writes to the JFS filesystems over NFS are
> much slower (1/5th) than the writes to the XFS filesystem over NFS. FTP
> transfers are much faster as well to any disk.
>
> I tried changing some of the NFS params but that didn't do anything. I even
> cleared one of the JFS disks and reformatted it to XFS and NFS writes sped
> up. AFAICT the only difference is the JFS filesystem.
>
> I googled but couldn't find anyone experiencing similar problems with NFS
> writes to a JFS filesystem.  Can anyone suggest a fix for this problem?
>
> Thanks
>
> John

One of the things that I can think of is poor fsync() performance for
JFS.  This is not a solution, but to test this theory, you could try
exporting with an async flag on the NFS server and see what kind of
performance you get with JFS vs. XFS.  If the async performance for
JFS and XFS is comparable, then you don't have too much of a choice.