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Controller Installation
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2.3 Configuring the Controller
This section provides information on configuring your controller.
NOTE :
The configuration examples provided here represent only a general guideline. These
examples should not be used directly to configure your particular controller.
The CLI (command line interface) commands used in these examples are fully
documented in sections 3.1 through 3.8—though exact commands may change depending
on your firmware version. To access the most up-to-date commands, use the CLI’s online
HELP feature.
2.3.1 Planning Your Setup and Configuration
Before proceeding with your controller configuration, determine the requirements for your SAN
environment, including the types of I/O access (random or sequential), the number of storage arrays
(LUNs) and their sizes, and user access rights.
The controller uses either an 8+2 or an 8+1+1 parity scheme. It is a unique implementation that combines
the virtues of RAID 3, RAID 0, and RAID 6 (Figure 2–3
). Like RAID 3, a dedicated parity drive is used
per 8+1 parity group; two parity drives are dedicated in the case of an 8+2 parity group or RAID 6. A
parity group is also known as a Tier.
This RAID implementation exhibits RAID 3 characteristics such as tremendous large block-transfer—
READ and WRITE—capability with NO performance degradation in crippled mode. This capability
also extends to RAID 6, delivering data protection against a double disk drive failure in the same tier with
no loss of performance.
Figure 2–3 Striping Across Tiers - RAID
However, Like RAID 5, this RAID implementation does not lock drive spindles and does allow the disks
to re-order commands to minimize seek latency, and the RAID 0-like functionality allows multiple tiers
to be striped, providing “PowerLUNs” that can span hundreds of disk drives. These PowerLUNs support
very high throughput and have a greatly enhanced ability to handle small I/O (particularly as disk
spindles are added) and many streams of real-time content.
LUNs can be created on just a part of a tier, a full tier, across a fraction of multiple tiers, or across multiple
full tiers. A minimum configuration for tiers of drives require either 9 drives in an 8+1 configuration or
10 drives in an 8+2 configuration. When configured in 8+1+1 mode, the tenth data segment is reserved
for global hot spare drives. When configured in 8+2 mode, spares may reside on each data segment and
are global only to that data segment.
Tier Configuration
Space Available
(Mbytes)Tier Disk Status Lun List
Capacity
(Mbytes)
ABCDEFGHPS
------------------------------------------------------------
2718202800121
ABCDEFGHPS2718202800122
ABCDEFGHPS2718202800123
0
0
0
---------------->
Parity Protection within same tier
----------->
Striping
across tiers
when a LUN
is created
across
multiple tiers