Hybrid drives hit NAS boxes

DNF claims that its Hyper Solid-State hybrid SATA or SAS drives each pack 20 times more performance than comparable 15,000 rpm drives. Power consumption, also, is 12.5W, which DNF says is 16% less power than 146 GB 15,000 rpm SAS disks, and 24% less than 15,000 rpm Fibre Channel drives.

The drives combine a 2.5-inch form-factor disk with the memory chip but the drives can fit into a 3.5-inch form-factor drive bay for compatibility with existing product lines. The drives will be made available early next week in all of DNF's storage products, which include the following: FlexStor-NAS Windows Storage Server NAS appliances; StorBank-XL and DataStor Linux-based NAS; DAS arrays based on SATA; entry-level Fibre Channel SAN storage arrays; IPBank IP SANs; and virtual tape libraries (VTL).

More on primary storage drives Fujitsu exec says SAS may take years to hit your array IBM, Seagate plan to rethink hard drives and memory SATA boosts RAID-6 use

"We had previously offered solid-state drives with our Flextor SSD NAS products," Ervin said. The solid-state disks were only available in 8 GB, 16 GB and 32 GB at a cost of $250 per gigabyte. "It wasn't affordable for a lot of our customers." Ervin added that the hybrid drives could be used to create tiers of storage within a box, with traditional SATA drives making up the bulk of capacity and the hybrid drives forming a Tier-1 layer for a transactional database or other performance-intensive application.

One area in which DNF cautions that the hybrid drives are probably not best suited is in IP SANs. "There's a tendency, if you get a lot of high-performance drives in an IP network, especially one that's not dedicated to storage, for the network overhead to negate the benefits of the drives," Ervin said.

Traditionally, storage platforms use RAM cache all in one place, usually at the controller. DNF says that its storage boxes will still also use centralized cache, but use the memory on the disks to further boost performance. DNF also claims that one of the chief benefits of splitting memory up among drives is that each drive will also have its own battery, making for better redundancy.

It's a claim disputed by at least one competitor. "It's great for speeding up [Windows] Vista, but as a write-back cache it seems a little questionable," said Tom Treadway, chief technology officer (CTO) of the storage software group at Adaptec Inc. "Our OEMs have always hated batteries -- you have to make sure they're charged before using them. And you have to deal with lifecycle issue, like batteries no longer holding a full charge, needing to be replaced every few years and then disposing of those batteries. And then there's the issue of unclean shutdowns where the write-back cache doesn't match the drives present at the next boot."

In response, Ervin said that customers have been asking for battery backups on the RAID cache.

"Most appliances don't pursue IO optimization or tuning at the drive or media level," said Brad O'Neill, senior analyst with the Taneja Group. "Any time you move away from the industry's de facto standard, you have a hurdle with customers -- the advantages have to significantly outweigh the customer's fear of moving off what's accepted."

Still, O'Neill pointed out, Copan Systems Inc. has had success with another unorthodox approach to SATA in MAID." Absolutely, it can happen," O'Neill said.

Several other companies are currently working on hybrid technologies, including consortiums of drive makers headed up by Seagate Technologies Inc. and Fujitsu Corp., as well as another group fronted by IBM that is looking to replace drives and memory altogether. So far, the other drive makers are focusing hybrid efforts on the consumer space, particularly in laptop PCs.