Disabling sequential read ahead can improve Samba performance significantly when there is a relatively high level of multiprogramming (many smbd processes or mixed with another workload), not an abundance of physical memory or slower disk technology. These can cause AIX to have a higher WAIT values. Disabling sequential read-ahead can also have an adverse affect on other workloads in the system so you will need to evaluate other applications for impact.

It is recommended to use the defaults provided by IBM, but if you experience a high amount of wait time, try disabling read-ahead with the following commands:

For AIX 5.1 and earlier: "vmtune -r 0"

For AIX 5.2 and later jfs filesystems: "ioo -o minpgahead=0"

For AIX 5.2 and later jfs2 filesystems: "ioo -o j2_minPageReadAhead=0"

If you have a mix of jfs and jfs2 filesystems on the same host, simply use both ioo commands.