Compaq 3000 manual Disk Drives

RAID Array 3000 Controller Shelf

From the storage shelf’s perspective, the controller receives the I/O requests from the host and directs them to the devices. Since the controller processes all the I/O requests, it eliminates the host-based processing that is typically associated with reading and writing data to multiple storage devices.

The controller does much more than simply manage I/O requests: it provides the ability to combine several ordinary disk drives into a single, high-performance storage unit called a storageset. Storagesets are implementations of RAID tech- nology, also known as a “Redundant Array of Independent Disks”. Every stor- ageset shares one important feature: whether it uses two disk drives or 12, each storageset looks like a single storage unit to the host.

You create storage units by combining disk drives into storagesets such as stripe- sets, RAIDsets, and mirrorsets, or by presenting them to the host as single-disk units (see Figure 2–3).

Figure 2–3 Logical Units Created from Storagesets, Partitions, and Disk Drives

Logical

Mirrorset

Logical

Unit

Unit

Partitioned

Storageset

Stripset

Raidset

Disk Drives	Striped
	Mirrorset
Logical	Partitioned
Unit	Disk Drive
	Logical
	Unit

2–4 EK–SMCPQ–UG. C01