Here’s a fun one. When you install a new power6 520 with multiple partitions you might want one of them to own the internal SAS raid controller. If you planned to use Raid5 then you purchased the auxiliary cache card. Now when you add the SAS controller to the partition profile, you would think that it would take the cache card along with it since: 1) you aren’t given a option to select the cache card and 2) where the heck else should it go?

 Well you would be wrong. When you get the system up and running, you may notice that the drives are running in DEGRADED mode. This means that the system doesn’t see the aux cache card and to protect you from a SAS controller failure, it is kindly running without using any disk controller cache. Did I mention that it probably took you a LONG time to get to this point?

 Solution: Take a look at the server properties and you will notice that you have the SAS controller in T9 allocated but there is also a “SCSI Bus Controller” in C9 not being used. The C9 component is actually the aux cache card for the SAS Raid controller. Use Dynamic Logical Partitioning to add the C9 physical adapter to your partition and all will be well.