NFS Services Administrator's Guide (5900-1632, August 2011)

See Installing and Administering LAN/9000 Software for information on troubleshooting LAN
problems.
3. If the timeout and badxid values displayed by nfsstat -rc are of the same magnitude,
your server is probably slow. Client RPC requests are timing out and being retransmitted before
the NFS server has a chance to respond to them.
Try doubling the value of the timeo mount option on the NFS clients. See “Changing the
Default Mount Options” (page 38)“Changing the Default Mount Options” on page 51.
Improve NFS Server Performance
□ Put heavily used directories on different disks on your NFS servers so they can be accessed
in parallel.
□ Enter the following command on the NFS server:
vmstat -n
If the us and sy values under cpu are high, and the id (idle time) value under cpu is close
to zero, your server’s CPU is heavily loaded. Try using a faster machine as your NFS server.
Do not use a gateway or a terminal server as an NFS or NIS server.
□ Enter the following command to determine which processes are using the most CPU:
/usr/bin/top
The top program sorts the processes running on your system, with the most CPU-intensive
process at the top of the display. It refreshes the display every five seconds. Try taking some
CPU-intensive processes off the server.
Type q to exit the top program.
□ Log into the NFS server and enter the following command:
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 38)“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.
100 Troubleshooting NFS Services