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?
Akemi