IBM disk queue_depth Parameter Adjustment

The queue_depth parameter affects disk I/O performance, especially in I/O intensive applications such as databases. You can adjust this parameter to improve the overall application performance. The following is how to adjust this parameter on AIX 5.3 and IBM ds4300.
Record the steps and precautions.

The following physical disk hdisk2 is based on the RAID 5 on IBM storage, which belongs to the VG datavg.

1. Back up datavg first. Make any adjustments in the production environment. Be sure to keep in mind that security first, backup is essential.
# Smit savevg

2. view the value of queue_depth on hdisk2 to be modified.
# Lsattr-El hdisk2 | grep queue_depth

3. First, the file system on umount datavg.
# Umount/U2

4. Vary off VG.
# Varyoffvg datavg

5. Delete the disk hdisk2.
# Rmdev-l hdisk2

6. Modify the disk hdisk2 queue_depth parameter.
# Chdev-l hdisk2-A queue_depth = 16 (this value is the specific queue_depth value to be modified)-P

7. Add disk hdisk2.
# Mkdev-l hdisk2

8. vary on VG.
# Varyonvg datavg

9. Mount the file system on datavg
# Mount/U2

10. Check whether the queue_depth parameter is successfully modified.
# Lsattr-El hdisk2 | grep queue_depth
As shown in the preceding figure, if the queue_depth value has been changed to the required value, the entire process is completed. If there are conditions, it is best to be heavy? Click machine. It should be noted that if this value is set improperly, it may cause the system to hang or crash. I personally
Because the value of waitqueue is too large, the system exception occurs. The INIT process always occupies about 20% of the CPU, syscal is more than K for a long time, and the waitqueue value is also high, seriously affecting the system performance.

Therefore, you should pay attention to monitoring for a period of time after adjusting this value until it is adjusted to a suitable value.