APC 15000 RAID manual Configuring the Controller, Planning Your Setup and Configuration

Controller Installation

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.

2.3.1Planning 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.

Striping across tiers when a LUN is created across multiple tiers

----------->

		Tier Configuration
	Capacity	Space Available
Tier	(Mbytes)	(Mbytes)	Disk Status	Lun List

------------------------------------------------------------

1	280012	271820	ABCDEFGHPS	0
2	280012	271820	ABCDEFGHPS	0
3	280012	271820	ABCDEFGHPS	0
	----------------	>

Parity Protection within same tier

Figure 2–3Striping 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.

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