Mixed Drives in the Mix

People confused about making decisions concerning Fibre Channel, SATA, and SAS drives might not have to choose between drives at all -- even in the same system. Then again, weeding the options could add to the confusion, at least initially.

For those seeking inclusive drives, many of the major SAN vendors have systems that mix Fibre Channel and SATA drives together. And when SAS drives ship late this year, these Fibre Channel/SATA hybrids will be able to take on those, too (see Report: SATA & SAS to Share Systems).

Hitachi Data Systems (HDS) last week followed EMC Corp. (NYSE: EMC)and IBM Corp. (NYSE: IBM), allowing SATA drives to be used in the same system as Fibre Channel drives (see Hitachi Launches SATA ).

The ability to use Fibre Channel and SATA in systems such as the Hitachi Thunder 9500V, EMC Clariion and NS700, and IBM FastT systems lets users store secondary and archived data on less expensive SATA drives without having to buy new disk arrays.

Of course, mixed systems cost more than SATA-only systems, but they could prove a happy medium for people looking for high-performance drives for mission-critical data and cheaper disk storage for the rest. The products also give administrators fewer systems to manage.Everyone was concerned about putting mission-critical data on SATA drives,” says The Yankee Group senior analyst Stephanie Balaouras. “With these systems, the first shelf is Fibre Channel and you can use the rest with SATA. You save on acquisition costs, and can use them for features like mirroring and backup.”

One thing: Fibre Channel and SATA drives now occupy different drawers or enclosures in disk systems. But future FC/SATA combination systems will allow mixing of both disks in the same Fibre Channel drawer, thanks to converter chips that will sit on the SATA drive. Converter chips are expected later this year from QLogic Corp. (Nasdaq: QLGC) and PMC-Sierra Inc. (Nasdaq: PMCS). Current systems use a bridging protocol that allows an FC-to-FC controller to talk to an FC-to-SATA controller.

SATA/SAS interoperability has one major drawback: SATA systems don't work from the same controllers as SAS drives, even though SAS drives can accommodate both SATA and SAS. Customers using SATA-only drives now will have to buy systems with SAS expanders later on for both to work together.

Also, even if SAS and SATA both thrive, Fibre Channel drives won't go away. The ability to use different drives in the same system will give all three types a place in storage.

“People think this is like sports, and they say, ‘SATA will wipe out Fibre Channel’ or ‘Fibre Channel will wipe out SATA,’ but one will not eliminate the other,” says Marc Staimer, president of Dragon Slayer Consulting. “Fibre Channel will come down in price to compete, and you’ll see SATA on the low end and Fibre Channel and SAS on the high end.”Staimer envisions sytems with SATA and SAS used for internal storage and systems with SATA and Fibre Channel for external storage.

Another emerging option is lower cost, lower performance Fibre Channel drives. HP was the first to announce such a drive, which it calls Fiber Attached Technology Adapted (FATA) (see EMC and HP Spin Disk). EMC has announced it will bring out what its EVP of storage platforms Operations Dave Donatelli calls “high-capacity, low-cost Fibre Channel drives in our high-end [Symmetrix] platform.” These drives spin slower and cost less than current Fibre Channel drives.

Unlike HP, EMC doesn’t call the drives FATA or label them a hybrid between Fibre Channel and SATA. Some find the FATA tag confusing.

“I don’t think they should’ve called it FATA,” Balaouras says. “They’re Fibre Channel drives with slower performance.”

Still, the drives will be provide another alternative -- which will likely add flexibility as well as confusion to drive choices.— Dave Raffo, Senior Editor, Byte and Switch