[CentOS] exports options

Sat Mar 24 21:41:36 UTC 2007
Akemi Yagi <amyagi at gmail.com>

I have been running a local repository on a CentOS4 server.  It serves
CentOS4 clients (and FC5, FC6, and SuSE10.x if I bother to mention).  My
current options for exports is (ro,wdelay,insecure,root_squash).  The ro
and insecure options were added manually and others are default.  I
understand 'sync' is the default although it is not shown by exportfs -v.
I also found this description in the NFS FAQ:

"For the Linux implementation of NFS Version 3, using the "async" export
option to allow faster writes is no longer necessary. NFS Version 3
explicitly allows a server to reply before writing data to disk, under
controlled circumstances. It allows clients and servers to communicate
about the disposition of written data so that in the event of a server
reboot, a Version 3 client can detect the reboot and resend the data.

In summary, be sure all exports on your Linux NFS servers use the "sync"
option by setting it explicitly or by upgrading your nfs-utils package to
version 1.0.1 or later. If you need fast writes, be sure your clients
mount using NFS Version 3. You may also improve write performance by
adding the "wdelay" option to your exports."

In other words, the default settings (sync and wdelay) seem to be the best
choice.  Is this generally true?  Are there any cases in which use of,
for example, async is more desirable?