Compaq 3000 User Manual

Page 37

RAID Array 3000 Controller Shelf

2–4

EK–SMCPQ–UG. C01

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
Unit

Mirrorset

Partitioned
Storageset

Stripset

Partitioned
Disk Drive

Striped
Mirrorset

Raidset

Disk Drives