A 3-tier ILM disk drive strategy has been announced by XioTech with 15K rpm Seagate Fibre Channel disks in the top tier, SATA drives in the third tier and something called Economy Enterprise drives in the mid-tier. You might think that's a second twist on the FC interface to ATA drives pioneered by HP with Hitachi GST and Seagate help, what HP calls FATA.

You would be wrong.

XioTech has been, with Seagate's help, much more ingenious. The top tier drives are Seagate 15K rm Fibre Channel drives with the full FC enterprise duty cycle capability and reliability, according to Rob Peglar, Xiotech's vice president of technology solutions.

Regarding the mid-tier drives he said, "Economy Enterprise drives are full Fibre Channel drives with the same reliability as the 15K rpm drives. However, they perform as if they are rotating at 7200rpm."

Interesting. He said 'perform as if'; so what speed do they rotate at? "They are rotating physically at 10,000rpm but the firmware has had multiple queuing taken away so they behave like a 7,200rpm drive."

Interesting again. It means Seagate has taken a 10K rpm drive and disabled firmware functionality to produce a cost-reduced FC drive for Xiotech. What is the result in price terms? Peglar says, "The Economy Enterprise drives have 300GB capacity and are priced less than the 15K drives, about 60 - 70 cents on the dollar versus the full enterprise Fibre Channel." That's about two thirds of the price.

And the bottom tier SATA drives? "They are somewhat less reliable than Fibre Channel (enterprise duty cycle) drives and are priced at 30 to 35 cents on the dollar compared to the enterprise Fibre Channel drives." About a third of the cost then leading to a neat tiered pricing scheme also.

Why not go the route of providing Fibre Channel access to SATA drives for the mid-tier? "We think that by offering the Economy Enterprise drives we give the user the full reliability of Fibre Channel drives. It's very important." The alternative route, that taken for example by FATA, "has used an ATA drive mechanism and sacrificed reliability," for cost. "We think we have the best of both worlds," and, "We think it's an excellent strategy."

We note here that Seagate is proving adept at developing specific drive versions for customers with FATA for HP and these effective speed-reduced drives for Xiotech. Perhaps we can expect more such customisations of commodity drives as disk manufacturers struggle to make sales in a market that seems to be over-supplied currently.

The Xiotech 3-layer ILM disk cake can be purchased in one chassis or the component tiers can be distributed across a cluster in separate chassis'.