AIO servers

If applications use asynchronous I/O on filesystem files, the OS uses the AIO subsystem. The number of AIO servers to start per CPU and the number of requests each server fills can be tuned with the smit fastpath “aio”. I usually set the number of request to 8192.

Adding a new JFS Log

If you have several busy JFS filesystems all using one log volume, there is contention for the JFS log; which slows down all the filesystems. You can either add another log to some of the filesystems, or switch to JFS2, which can put the log inside each filesystem. To add another log:

Validate mirroring for splitvg

Splitvg is a really cool feature of AIX 5L, but there is one problem. Each “copy”, must be on a different set of disks. Mirrored copies of each LV are numbered 1, 2, or 3 (1 for the first copy, 2 for the second, and 3 for the third). Splitvg has to be told which “copy” to split and recreate as a new VG. So, this means that all of the #1 copies must be on the same disks, and all of the #2 copies must be on different disks. Splitvg isn’t smart enough to work around this. So, there’s a quick little script to run on each PV in the volume group, if it’s all okay there won’t be any output: