Performance Tuning

Issue the following command to check your server’s memory utilization:

netstat -m

If the number of requests for memory denied is high, your server does not have enough memory, and NFS clients will experience poor performance. Consider adding more memory or using a different host as the NFS server.

Put heavily used directories on different disks on your NFS servers so they can be accessed in parallel.

Make sure your server is running the correct number of nfsd processes. See “Adjust the Number of nfsd Processes”.

Issue 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.

Issue 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 issue 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 file system 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.

	CAUTION: Do not remove symbolic links in an NFS diskless environment. File sharing in NFS diskless is done by means of symbolic links.

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”.

Export directories with the async option. When async is specified, the server acknowledges write requests from clients before writing data to disk. Clients do not have to wait for a write request to complete before issuing another request.

Issue the ps -ef command to make sure four biod processes are running on each client. To start four biod processes, set the NUM_NFSIOD variable to 4 in the /etc/rc.config.d/nfsconf file, and issue the following command:

/usr/sbin/biod 4

	NOTE: If your performance bottleneck is a slow server, increasing the number of biod processes beyond four will not improve NFS performance, and it might make it worse.

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. See “Changing the Default Mount Options”.

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. See “Changing the Default Mount Options”.

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). See “Changing the Default Mount Options”.

Type the following command on the NFS server, to find out the block size of the server’s file system:

/usr/sbin/tunefs -v devicefilename

On the NFS clients, set the wsize and rsize mount options to the bsize value displayed by tunefs. See “Changing the Default Mount Options” .

On the NFS clients, look in the /etc/fstab file for “stepping-stone” mounts (hierarchical mounts), as in the following example:

thyme:/usr /usr nfs defaults 0 0
basil:/usr/share /usr/share nfs defaults 0 0
sage:/usr/share/lib /usr/share/lib nfs defaults 0 0

Wherever possible, change these “stepping-stone” mounts so that whole directories are mounted from a single NFS server.

Stepping-stone (hierarchical) mounts, like the one in the example above, cause more NFS requests than mounts from a single server. In the example, if a client wants access to something in /usr/share/lib, a request must be sent to server thyme, then to server basil, and finally to server sage.

Issue the following command to check the size of your transaction log:

/usr/lib/nis/nislog | head -10

If your transaction log is fully checkpointed, it will contain only three entries. If it contains many entries, issue the following command to checkpoint it:

nisping -Ca

The nisping -C command can cause a long delay if your namespace is large. Do not reboot the system. Do not reenter the nisping command. This problem will solve itself. Just wait until the server finishes checkpointing.

Make sure your NIS_PATH environment variable is set to something clean and simple, like org_dir.$:$. A complex NIS_PATH value, particularly one that contains a variable, will slow your system and may cause some operations to fail. See “Change the Search Order of Domains”.

Concatenation paths in tables slow performance. If performance is a problem in your NIS+ namespace, do not use concatenation paths. See “Create or Remove Paths Among Tables”.

Make sure you have 10 or fewer replica servers per domain.

NIS+ groups that contain other groups (recursive groups) slow NIS+ performance. If performance is a problem in your NIS+ namespace, do not use recursive NIS+ groups. See “Add or Remove Members of an NIS+ Group”.

Large transaction logs slow NIS+ performance, particularly at system startup. If your transaction logs are large, or if you have just run the nispopulate script to populate your domain tables, issue the nisping -Ca command to checkpoint your directories. Make sure your master server has a cron job scheduled to issue the nisping -Ca command daily. Type man 1 crontab for information.

Issue the ps -ef command to make sure nis_cachemgr is running on every NIS+ client host. Start it if it is not. Type man 1M nis_cachemgr for information.

An NIS+ lookup command like niscat returns the error message

Server busy. Try again.

for one of the following reasons: