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.

Just a collection of semi-usefull commands.

If the MTU size on all nodes in a HACMP cluster do not match, the cluster will NOT start. Check with “netstat -i”.

On AIX 4.3+, IP aliases are stored in the ODM, this is much better than hacking the /etc/rc.net script. Removing the IP alias from the ODM isn’t quite so obvious.

Sometimes you want to just restore a single file from a mksysb:

Sometimes using a RAM disk makes sense. I haven’t tested these commands with a recent OS, but here are the steps. Run the following commands to setup a Ram Disk, the disk will not be recreated after bootup:

Okay, this is really easy since they added the mirrorvg command, but here’s the checklist anyway:

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:

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: