I have a few questions about LVM and ssm
1. The first question is with LVM is it best to have multiple volume groups or as few as possible. So lets say I add two hard-drives to a server. One I will call rhapsody and one I will call rhapdata. They are two different physical hard-drives, but they will be used by the same program. Should I add them to the same volume group/pool?

2. When I try to add a 15gb hard-drive and I run the ssm create command and specify to add 15gb it fails saying that basically there isn't enough space. Or that there are 4095 extents when 4096 is needed. So when using the create command do I have to specify a little bit smaller then the size of the actual hard-drive?

Regarding LVM: A volume group is just a storage pool from which you can allocate logical volumes. It depends on your application's logic, but chances are it only needs a single VG.

From your description, I gather that your app needs two logical volumes named rhapsody and rhapdata. You can create two such logical volumes from a VG that consists of one, two or more disks. My point is, the number of hard disks is entirely unrelated to the number of volumes (and that's also one of the major points of LVM).

I haven't heard of ssm.

In larger installations, I commonly see volume groups being assigned to help reflect "where the disk drives actually are." (And by extension, what I/O channels service them.) The I/O workload is generally apportioned between the different storage units according to purpose and characteristics. Logical Volumes then allow the storage in each area to be allocated and re-allocated conveniently.

1. If you require (physical) separation, use separate pools. For flexibility of data placement, put both drives in the same pool. Only you can make that decision.

2. Don't specify size - let the system determine what's left after formatting overheads are taken into consideration. ssm being a management layer on top of (possibly multiple different) storage backend(s)