Delivering the goods.(RAID(redundant array of independent disks) controllers)(Promise Fast Trak TX4310 versus Promise Supertrak EX83500 )(Product/service evaluation)

Byline: Gordon Laing

Delivering the goods

Find out how software and hardware-based Raid controllers perform

In recent Performance columns, we compared the features and performance of several popular Raid technologies using up to four hard disks. This month we're following up those reports with tests using a more sophisticated hardware Raid controller.

Software vs hardware

Many motherboards and budget host adapter cards offer the choice of Raid Levels 0, 1 or 5. Raid 1 makes an identical copy of one disk on another to provide 100 per cent redundancy, albeit at the cost of half the total capacity and slower speed than Raid 0. Raid 5 uses three or more disks and delivers 100 per cent redundancy by writing parity data on all of them. The advantage over Raid 1 is only losing one disk worth of capacity to redundancy.

Raid 5 sounds ideal, but the calculation of parity data is complex and normally offloaded to your main processor by common motherboard controllers. It may be cheap to implement, but it results in greater overheads on your main CPU and often very poor write-speeds.