Improving filer performance

About this section

This section describes configuration procedures that might improve your filer's performance.

Balance NFS traffic on network interfaces

Attach multiple interfaces on the filer to the same physical network to balance network traffic among different interfaces. For example, if two Ethernet interfaces on the filer named toaster are attached to the same network where four NFS clients reside, specify in /etc/fstab on client1 and client2 that these clients mount from toaster-0:/home. Specify in /etc/fstab on client3 and client4 that these clients mount from toaster-1:/home. This scheme can balance the traffic among interfaces if all clients generate about the same amount of traffic.

The filer always responds to an NFS request by sending its reply on the interface on which the request was received.

Avoid access time update for inodes

If your applications do not depend on having the correct access time for files, you can disable the update of access time (atime) on an inode when a file is read. Set the no_atime_update option to On for each volume to prevent updates. Consider turning this option on if your filer has extremely high read traffic, for example, on a news server used by an Internet provider, because it prevents inode updates from contending with reads from other files.

Caution
If you are not sure whether your filer should maintain an accurate access time on inodes, leave this option set at its default, Off, so that the access time is updated.

Improve read-ahead performance

If the file access patterns of your clients are random (nonsequential) and the cache age is less than 3, setting minimal read-ahead to On might improve performance. By default, the filer uses aggressive read-ahead, which enhances sequential access, and is more commonly used by UNIX clients and applications. Use the sysstat command to determine the cache age. Set the minra option to On for each volume to specify minimal read-ahead. By default, the option is set to Off and the filer does very aggressive read-ahead.

Add disks to a disk-bound volume

If you have a single-volume filer, use the sysstat -u command to determine the fraction of time that the busiest disk is active. If the fraction is greater than 80 percent, add disks to the volume using the vol add command.

Make optimal use of Slot 8

This method of improving filer performance applies to F700 series filers only. The fastest available PCI slot in an F700 series filer that is not clustered is Slot 8. If your filer uses a 64-bit network interface card, put it in Slot 8 to take advantage of the speed. If the filer does not use a 64-bit network interface card, put the main FC-AL adapter in this slot.

Put cards in correct slots

At boot time or when you use the sysconfig -c command, you might see messages that expansion cards must be in certain slots. To improve performance, follow the recommendations in the message. See the System Configuration Guide at http://now.netapp.com/NOW/knowledge/docs/hardware/syscfg/ for recommended card placement.

Maintain adequate free blocks and free inodes

If the percentage of free block or free inodes falls to less than 10 percent on any volume, the performance of writes and creates can suffer. Check free blocks and inodes using the df command and df -i command, respectively. If the percentage of used blocks is greater than 90 percent, increase blocks by adding disks or deleting snapshots. If the percentage of free inodes is less than 10 percent, increase inodes by deleting files or using the maxfiles command.

Use oplocks for CIFS filers

Oplocks allow CIFS clients to cache more data locally. This reduces traffic to the filer. On a filer running CIFS that is not in a database environment, set oplocks to On using the options cifs.oplocks.enable on command. If the filer is in a database environment, ensure that the oplocks are not set.

Increase the TCP window size for CIFS

Increasing the TCP window size to its maximum setting on both the filer and the CIFS client can improve performance for large transfers. The TCP window size controls the number of TCP messages that can be transmitted between the filer and CIFS client at one time. The filer supports a maximum window size of 64,240.

Use the cifs.tcp_window_size 64240 command to maximize the TCP window size on a filer running CIFS. Use the nfs.tcp.recvwindowsize 64240 command to maximize the TCP window size on a filer running NFS. Change the window size in the Windows registry on a Windows NT client by adding the DWORD value \\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services \Tcpip\Parameters\TcpWindowSize and set it to 64,240 (0xFAF0 in hexadecimal).

Back up using qtrees

If your filer has multiple tape drives and a volume that has two to four qtrees, you can improve backup rates by running multiple dump commands in parallel, each reading a different qtree and writing to a different tape drive.