WD Designs RAID Drive

Western Digital Corp. has designed a disk drive specifically targeted for RAID and other heavy-duty cycle applications.

WD, based in Irvine, Calif., said Tuesday that it has begun shipping the WD Caviar RAID Edition (RE) drives, a family of three 3.5-inch, 7,200-RPM drives ranging in capacity from 120GB to 260GB.

The drives are specifically designed to challenge competitors like the Maxtor Corp. MaxLine drives, which are rated for non-I/O-intensive low-duty cycles. By contrast, the WD Caviar RE drives are rated at 1 million hours mean time before failure (MTBF), running nonstop.

Interestingly, WD designed the Caviar RE in response to a batch of 250GB desktop and server drives the company launched about a year ago, said Hubbert Smith, director of enterprise marketing for Western Digital. Customers quickly tried plugging the drives into RAID arrays, where they suffered mechanical failures.

“Desktop drives dont stand up in those kind of environments,” Smith said.

The redesigned RE drives now undergo the same burn-in cycle as the companys high-end Raptor drives, Smith said. Customers began testing the drives this past March, giving them a thumbs-up for production.

Meanwhile, drive makers and storage vendors both are encouraging the use of RAID arrays, which use redundant disks to mirror information as well as “stripe” a file to maximize read performance. In a RAID 50 array, a “hot swap” drive also exists to replace a failed drive. When the failed drive is removed, the existing information propagates across the other drives.

During this period of “healing,” the array is also vulnerable; if a second drive goes down, data can be irretrievably lost. WD set out to minimize this recovery time with a technique called time-limited error recovery, which takes into account the ability of modern drives to do self-diagnostics and repair or exclude damaged sectors.

Using the WD technology, a drive will typically drop off the RAID array for about 30 seconds to adjust its sectors, Smith said; the maximum time is about five minutes.

The three-platter design will offer lower power metrics than its five-platter competitors, Smith said. The drive consumes 8.2 watts reading and writing, 11.5 watts seeking data, and 16.2 watts spinning up. Acoustic power will range between 28 and 33 dB, depending on the function, WD said.

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