Using mirrors to boost storage performance
By Linda Gail Christie
A hard disk, by its very nature, is susceptible to failure. Because the loss of data and downtime can be very costly, many IT departments employ RAID level 1 mirrored drives to ensure availability. If any drive in a mirrored set fails, that drive's mirror will continue to operate, keeping applications and data available. However, purchasing two drives to provide the capacity of one, is costly.
To help offset these costs, various read operations have been devised to capitalize on the fact that duplicate data resides on two disks. In a typical SCSI configuration, for example, Disk A reads the outer tracks while Disk B reads the inner tracks to shorten seek times and boost throughput. 3ware Technologies has taken this strategy one step further by developing intelligent algorithms that detect which head is closest to the data needed, reducing head-seeking latency delays while enabling access to the entire disk.
"Our TwinStor controller architecture utilizes a statistical history of data access to reorder and assign requests to the optimal drive," said Dave McAllister, 3ware's director of software marketing. "In addition, it can use both drives together to mimic RAID-0 striping speeds for downloading large files or delivering streaming video, while retaining the fault tolerance of RAID-1 mirroring."
In an independent evaluation, National Technical Systems (the leading provider of certified testing and IT solutions in the industry) reported that 3ware's Escalade(TM) packet-switched RAID controllers, using ATA/100 disk drives, exceeded the theoretical limitations of Ultra160 SCSI with sequential read performance of 163MB/s.
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About the author: Storage management tips are written by Linda Gail Christie, a contributing editor based in Tulsa, Okla.
