IBM 88861TU, Planning Manual

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Use the following considerations when planning for storage pools:
v
All hard disk drives in a storage pool must be the same type, and a disk drive
can only belong to one storage pool.
Note: When installing SAS RAID controller modules in a BladeCenter S chassis,
you must use SAS hard disk drives. SATA hard disk drives are not supported.
v When determining which hard disk drives are in a storage pool, you should use
hard disk drives from both storage modules (if both are installed) to maintain
the highest availability. For example, if you are implementing a RAID 1 storage
pool, consider using a hard disk drive in one storage module and mirroring that
drive to a hard disk drive in the other storage module.
You can choose from the following RAID implementations when defining storage
pools:
Important:
RAID 0
Also known as a striped set or a striped volume, a RAID 0 implementation
stores data evenly across two or more hard disk drives. No data
redundancy is available. To implement RAID 0, you must use at least 2
hard disk drives.
You can implement RAID 0 with hard disk drives of different sizes.
However, the storage space added to the storage pool be each disk is
limited to the size of the smallest disk. For example, if you implement
RAID 0 with a hard disk drive that is 120GB and a hard disk drive that is
100GB, the total size of the storage pool is 200GB.
RAID 1
A RAID 1 implementation creates an exact copy of data (also called
mirroring) on two or more hard disk drives. Each hard disk drive in the
storage pool contains a complete copy of the data and it can be addressed
independently.
RAID 5
A RAID 5 implementation uses block-level striping with parity data
distributed across all hard disk drives in the storage pool. You can increase
the number of hard disk drives in the storage pool dynamically. To
implement RAID 5, you must use at least 3 hard disk drives.
RAID 1+0
A RAID 1+0 implementation combines the function or RAID 0 with the
function of RAID 1. Drives are mirrored and data is striped across those
drives. To implement RAID 0+1, you must use at least 4 hard disk drives.
Defining volumes
After you define storage pools, you need to break the storage pools into discrete
areas of storage, which are called
volumes . Each blade server can access one or
more of these volumes.
Chapter 4. Planning for configuration
67