For a write-intensive server, the following procedures can improve the speed of disk writes:
You can increase the speed and efficiency of disk cache writes by increasing the number of write requests that can be executed at one time.
To determine whether you must increase the number of concurrent writes, first compare the number of dirty cache buffers to the total number of cache buffers. These statistics are found on the General Information screen in the monitor utility. Dirty cache buffers contain data that has not yet been written to disk.
The ratio of dirty cache buffers to total cache buffers is an indicator of the efficiency of disk cache writes. If the number of dirty cache buffers is greater than 70% of total cache buffers, increase the number of concurrent write requests.
NOTE:Increasing the number of concurrent disk cache writes slows disk cache reads. You might want to balance the speed of disk writes and reads to meet the needs of users. If your server’s processing load is write-intensive, you can favor disk writes. If it is read-intensive, favor disk reads.
Increase the value of , using SET
in the NW 6.5 SP8: Utilities Reference. The new setting is persistent through a server reboot. If the parameter is currently at the default value of 50, try increasing it to 100.
Change the parameter for faster writes if network users frequently make many small write requests and the server is slow to respond to the requests. Use SET
in the NW 6.5 SP8: Utilities Reference to modify the following parameters:
Increase the value of the parameter.
This parameter specifies how long the system waits before writing a not-completely-dirty cache buffer to disk.
If the value is low, the system writes to disk more frequently, but writes fewer requests each time. If the value is high, the system waits longer before writing to disk, but executes more write requests with each operation. A higher value provides greater efficiency in writing to disk.
If the parameter is currently at the default value of 3.3 seconds, try increasing the value to 7 seconds.
Increase the value of the parameter.
This parameter specifies how long the system keeps a directory table write request in memory before writing it to disk.
IMPORTANT:Increasing the parameter provides slightly faster performance, but can increase the chance of directory tables becoming corrupted.
If the parameter is currently at the default value of 0.5 seconds, try increasing the value to 2 seconds.
Increase the value of the parameter.
This parameter determines how many write requests from directory cache buffers are executed at one time. Increasing this value increases the efficiency of directory cache write requests.
Increasing the number of concurrent directory cache writes decreases the speed of directory cache reads. Balance the speed of writes and reads to meet the needs or your users.
If the parameter is currently at the default value of 10, try increasing the value to 25. The changed value is now persistent.
Read-after-write verification is almost always provided by the hard disk. If your hard disk provides read-after-write verification, you might want to disable the software version of read-after-write verification in order to nearly double the speed of disk writes.
WARNING:Turning off read-after-write verification can increase the risk of data corruption on the server’s hard disk. You should use the following procedure only if your disks provide read-after-write verification and are reliable, or if your disk subsystem provides data fault tolerance through mirroring.
Hard disks that provide their own means of read-after-write verification.
Use the SET
command as described in the NW 6.5 SP8: Utilities Reference to disable the parameter.