A new backup plan

In an ideal world, all federal data center managers would be able to back up their disk storage systems to secondary disks, which allow for faster, more flexible data restoration than the tape-based backup systems typically used. But the disk systems are several times more expensive than equivalent-capacity tape systems, so at most agencies, it's tape or nothing.

But a new class of enterprise disk systems might spur federal information technology managers to rethink the cost equations behind those long-standing assumptions. Using arrays of inexpensive Advanced Technology Attachment (ATA) hard drives, which until recently have been used primarily in desktop PCs, storage vendors such as Nexsan Technologies and 3ware Inc. are offering enterprise storage systems that shrink the price gap between disk and tape.

The ATA disk arrays include many of the fault-tolerant features associated with high-end storage, such as hot-swappable disks that can be replaced without bringing the system down and data protection through Redundant Array of Independent Disks (RAID) technology.

Backing up to disk instead of tape "gives customers the chance to change their backup paradigm and get better performance and data protection at a really cheap price, which is where ATA comes in," said Tony Prigmore, senior analyst with Enterprise Storage Group, a market research firm.

In part because they are manufactured in large quantities, ATA disks are one-third the price or less than the Fibre Channel or SCSI disks that are typically used in enterprise storage systems. Initially, though, the ATA array vendors are positioning their products as replacements not for the high-end disk systems used for primary storage, but rather for the tape systems used to back up the online data.

Due to its low cost per megabyte, tape has long been the medium of choice for the two main backup applications: quick system restoration and long-term archiving. ATA vendors say system restoration is where their products will provide the greatest benefits.

"The advantage of disk-based backup is that disk has a faster retrieval rate than tape," said Dave Hill, research director for storage and storage management at the Aberdeen Group Inc. "Also, disks store randomly, so they can retrieve specific files quicker than tape, which stores data sequentially."

Diamond Lauffin, senior executive vice president at Nexsan, claims that the total cost of his company's ATA-based InfiniSAN D2D, or disk-to-disk, backup solution is actually less than a comparable solution using an automated tape library.

For example, Lauffin said Nexsan's eight-drive ATAboy RAID array, which comes with the D2D backup software and can store up to 560G of data, costs $8,500. On the other hand, he said that a 12-tape library with two drives and about 600G of storage capacity might cost around $14,000, which doesn't include the several thousand dollars extra for backup software.

Costly Archives

For now, ATA arrays don't make as compelling a cost case for storing large amounts of data for archival purposes, according to Dan Tanner, a senior analyst at the Aberdeen Group. In that application, data backups are stored on the least expensive, removable media, such as tape cartridges, and then placed in a safe, off-site location. The tapes can be retrieved if a disaster such as a flood or fire destroys the primary data center; quick system restorations are not the highest priority. Nonetheless, Tanner thinks ATA arrays might even gain some ground in that area.

"ATA is inexpensive, so you can start to think about removable disks," he said. "And with [the new] Serial ATA disks coming, it will be very easy to have removable disks that are nondisruptive." (See "Serial solution," above.)

ATA array vendors currently use custom software to give their products a hot-swappable disk capability. That's a good example of the work they have done to build disk arrays using a technology originally developed to connect one or two hard disks to the motherboard inside a personal computer.

ATA has been around in one form or another for about 15 years and is also known as IDE, or Integrated Drive Electronics, because the controller is integrated right on to the disk drive itself. The vast majority of disk drives manufactured each year are ATA, according to market researcher IDC.

ATA arrays are currently available only from a handful of smaller disk-storage vendors. But Prigmore thinks that "once these early adopters gain traction, there's no reason why the big guys won't make the same shift" and begin to offer ATA arrays as well.

That may be the case, but at least one large storage vendor suggests otherwise. A spokesperson for Dell Computer Corp.'s storage division said the company doesn't have any plans to build ATA-based storage systems.

Kevin Connors, senior director of product marketing for 3ware, thinks the large storage companies will not rush to offer ATA for the same reason they have not offered it to date: It's just not profitable enough.

"It's very difficult [for manufacturers] to design a product that reduces their [average selling price] and margin contribution while still maintaining the same level of value," he said.

Regarding concerns about reliability and performance, ATA array vendors say that field data for ATA drives show that they are as reliable as SCSI or Fibre Channel drives. As for performance, Prigmore said backup applications don't need the fastest disk speed available, and in any case, the means by which an array's RAID controller moves data across multiple drives mitigates any speed disadvantage among the various disks.

But 3ware's Connors said those are the types of concerns that ATA array vendors must overcome to get their message out.

"A lot of customers consider the ATA world as the disk drive in the PC that their family uses at home, and that doesn't fit in the enterprise," he said. "We've had a lot of education and evangelism to do in the last year and a half, but it's starting to take hold."