Backing up disk to disk

“My Access file is corrupt. Can you restore it for me?” Such common user requests can send administrators on a merry chase that includes digging through archived tapes, inserting the correct cartridge into the tape loader and then sequentially searching through it to restore the user’s data. The process can easily take a half hour or more of an administrator’s time.

A new generation of relatively low-cost disk-to-disk backup systems is changing all that, reducing the restoration task to a 30-second point-and-click affair. It’s so simple, in fact, that users can do it themselves.

“It’s slick,” says Bob Kennedy, director of computer resources at construction firm The Newtron Group Inc. in Baton Rouge, La. Newtron is an early adopter of the InfiniSAN D2D backup appliance from Los Angeles-based NexSAN Technologies Ltd. The 500GB system, which cost US$11,200 installed, has cut the administrative time required for file restores, Kennedy says. “Now you just click Restore and it’s back,” he says.

“The reality of having your backup information on random-access media will change how people interact with their backups,” says Chris Bennett, director of platforms and systems at Network Appliance Inc. in Sunnyvale, Calif. “We’re on the very front end of what is going to be a revolution in the way people deal with backup issues.”

These disk-based backup systems use the Advanced Technology Attachment (ATA) interface internally but present a SCSI, Fibre Channel or Gigabit Ethernet face to the outside world. Devices may support data transfers in block or file format.

Cost is the driving factor behind the trend. ATA-based disk drives aren’t new and are common on the desktop. Manufacturing economies have driven prices down to $15 to $20 per gigabyte, making them competitive with high-end tape subsystems. And while the functionality of ATA drives can’t compare to SCSI’s reliability and performance as a primary storage medium, they’re well suited to streaming and large block transfers.

“Once you get the head in the right place, you can move [the data],” says Bennett.

The systems can also help solve the problem of shrinking backup windows by acting as an inexpensive intermediate cache between the target storage and the tape subsystem. And since software tools like Network Appliance’s SnapVault can update the backup indefinitely without re-creating the primary backup image, the appliances can back up storage in remote offices over a wide-area network. This lets archival tape copies be created and managed centrally.

Newtron’s backup appliance backs up PeopleSoft and SQL Server data residing in its main office across an interbuilding fiber link. “If our [main] office burned, everything would be out there on the NexSAN,” Kennedy says.

Vendors are also promoting the devices as a general-purpose repository for “near-line,” or secondary, storage. For example, third-party software allows Exchange e-mail documents to be migrated to a NearStor device from Network Appliance as they age, without changing their appearance to the end user.

“We’re already seeing a change in the way backup technology works,” says Nancy Marrone, an analyst at The Enterprise Storage Group Inc. in Milford, Mass. In the future, she says, backup software will include more hierarchical storage management capabilities and the intelligence to “determine what data needs to be backed up to disk vs. tape and when.”

Product Pipeline-Three Takes on Backup Appliances

Of the many vendors that are now marketing devices as disk-to-disk backup appliances, these three represent the different approaches and price ranges.

NexSAN Technologies

This start-up was one of the first to market last fall when it announced the InfiniSAN D2D, an ATA-based disk-to-disk backup appliance. Its software functions as a versioning system that allows copying of incremental updates via the Network File System or Common Internet File System protocol. Special “agent” software can automate backups for specific applications.

Quantum Corp.

The Milpitas, Calif.-based disk vendor takes a more pragmatic approach with its DX30. The system, slated to ship in the second half of this year with 3TB of storage and a price tag of $45,000, emulates a tape library to allow compatibility with existing backup software and the backup policies that users have created with them.

Quantum claims that its approach gains efficiencies by streaming data blocks directly between disks over a Fibre Channel storage-area network. Although backups and restores are faster, this approach uses software designed to stream to a serial tape medium to perform backups, and restores to a random-access medium.

Network Appliance

This storage heavyweight has taken the high end with the recent shipment of its $275,000, 12TB NearStor R100 backup appliance. The system puts a filer on a rack full of hot-swappable 160GB ATA drives and supports familiar Network Appliance tools such as SnapVault, which can indefinitely update a backup image without having to establish a new baseline.

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