NFS Services Administrator's Guide (B.11.31.03) August 2008

nfsstat -s
If the number of readlink calls is of the same magnitude as the number of lookup
calls, you have a symbolic link in a filesystem that is frequently traversed by NFS
clients.
On the NFS clients that require access to the linked directory, mount the target of
the link. Then, remove the link from the exported directory on the server.
When a client requests access to a linked file or directory, two requests are sent to
the server: one to look up the path to the link, and another to look up the target of
the link. You can improve NFS performance by removing symbolic links from
exported directories.
□ If the value of getattr displayed by nfsstat -s is greater than 60%, one or
more clients have either turned off attribute caching (with the noac mount option)
or set the caching timeout values too low.
Increase the attribute caching timeouts on the clients that have them set below the
default values. See “Changing the Default Mount Options” (page 55)“Changing
the Default Mount Options” on page 51.
□ Share directories with the async option. When async is specified, the server
acknowledges write requests from clients before writing data to a disk. Clients do
not have to wait for a write request to complete before issuing another request.
This can be performed only for NFSv2. The default option for NFSv3 is async.
Improving NFS Client Performance
□ For files and directories that are mounted read-only and never change, set the
actimeo mount option to 120 or greater in the /etc/fstab file on your NFS
clients.
□ If you see several “server not responding” messages within a few minutes,
try doubling the value of the timeo mount option in the /etc/fstab file on your
NFS clients.
□ If you frequently see the following message when attempting access to a
soft-mounted directory,
NFS operation failed for server servername: Timed out
try increasing the value of the retrans mount option in the /etc/fstab file on
the NFS clients. Or, change the soft mount to an interruptible hard mount, by
specifying the hard and intr options (the defaults).
□ Enter the following command on the NFS server, to find out the block size of the
server’s filesystem:
/usr/sbin/tunefs -v devicefilename
Performance Tuning 139