Drive Arrays and Fault Tolerance

Table D-2: Choosing a RAID Method

Most Important

Also Important

Suggested RAID Level

Fault tolerance

Cost effectiveness

RAID ADG*

 

 

 

 

I/O performance

RAID 1+0

 

 

 

Cost effectiveness

Fault tolerance

RAID ADG*

 

 

 

 

I/O performance

RAID 5 (RAID 0 if fault

 

tolerance is not required)

 

 

 

 

 

I/O performance

Cost effectiveness

RAID 5 (RAID 0 if fault

 

tolerance is not required)

 

 

 

 

 

 

Fault tolerance

RAID 1+0

 

 

 

*Not all controllers support RAID ADG.

Other Fault-Tolerance Options

Your operating system may also support software-based RAID or controller duplexing.

•Software-based RAID resembles hardware-based RAID, except that the operating system works with logical drives as if they were physical drives. To protect against data loss caused by physical drive failure, each logical drive must be in a different array from the others.

•Controller Duplexing uses two identical controllers with independent, identical sets of drives containing identical data. In the unlikely event of a controller failure, the remaining controller and drives will service all requests.

However, the hardware-based RAID methods described in this appendix provide a much more robust and controlled fault-tolerant environment. Additionally, controller duplexing and software-based RAID do not support online spares, auto-reliability monitoring, interim data recovery, or automatic data recovery.

If you decide to use one of these alternative fault-tolerance options, configure your arrays with RAID 0 for maximum storage capacity and refer to your operating system documentation for further implementation details.

HP Smart Array 641/642 Controller User Guide

D-11