Think Disk, Not Tape, for Server Backups

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A new class of enterprise backup solutions may just prompt you to rethink the cost differences between using disk rather than tried and tried true, inexpensive tape for backing up servers.

Until recently, desktop PCs used Advanced Technology Attachment (ATA) hard drives, which provide many of the fault-tolerant features associated with server storage, such as RAID. Now, storage vendors, such as Nexsan Technologies, Los Angeles, California; and 3ware, Mountain View, California; are betting that ATA disk arrays will lower your cost of using disk for server backups.

Backing up to disk instead of tape will undoubtedly give you a chance to change your backup paradigm and get better performance and data protection at a lower price, according to John Webster, senior storage analyst for The Illuminata Group, Nashua, New Hampshire.

Because ATA disks get manufactured in large quantities, they cost about one-third the price or less than the cost of fibre channel disks or SCSI disks that typically appear in enterprise storage systems. The current crop of ATA array vendors are positioning their products as replacements for tape systems used to backup online data, rather than as replacements for the high-end disk systems used for primary storage.

As a result of the low cost per megabyte, tape has been the medium youre most likely to select for two main backup applications quick systems restores and long-term archiving. ATA vendors say system restores are where their products will provide the great benefits.

Webster says that disk-based backups provide a faster restore rate than using tape. He adds since disks store data randomly, they can retrieve specific files quicker than tape, which stores data sequentially.

You might find Nexsans InfiniSAN D2D, or disk-to-disk, backup system to be less than a comparable system using an automated tape library. For example, Nexsans eight-drive ATAboy RAID system, which comes with D2D backup software, costs about $8,500 and can store about 560 gigabytes of data. In contrast, a Nexsan source says a 12-tape library with two drives costs about $14,000 and offers about 600 gigabytes of storage capacity. Of course, you also have the cost of backup software and tons of tapes.

For now, some industry analysts say that ATA arrays dont make as compelling a cost for storing terabytes of data for archival purposes where restoring data quickly isnt your top priority. Dan Tanner, a senior storage analyst at the Aberdeen Group, Boston, Massachusetts, says that for this type of application, youd typically want to store data on the least inexpensive media, such as tape cartridges, and then store the tapes in an off-site secure facility. You can retrieve the tapes if a disaster, such as a fire, destroys the primary data center. Tanner adds that ATA arrays could gain some ground in applications where the ability to restore data is a top priority.

ATA vendors use custom software to give their products a hot-swappable disk capability. Thats a good example of the work theyve done to build disk arrays using a technology developed to connect one or two hard disks to the motherboard inside a personal computer.

ATA technology has existed for about 15 years, and is also known as IDE or Integrated Drive Electronics, because the controller is part of the disk drive itself. ATA disk drives make up the majority of disk drives manufactured each year, according to International Data Corp., Framingham, Massachusetts

Right now a handful of emerging companies offer ATA arrays. The jury is out as to when the well-known storage vendors will be going with them. However, a source at Dell Computer Corp., says his company has no means to build ATA-based storage systems. Kevin Connors, senior product marketing director at 3ware, says that large storage companies right now perceive that its not profitable for them to offer ATA arrays.

Meanwhile, ATA array vendors say that their field tests of ATA drives show they are as reliable as SCSI or fibre channel drives.

Likewise, new features of the newly released Serial ATA technology will help ATA array vendors to build products that are even better suited for disk-to-disk backup and other enterprise storage applications. These features include the following:

— potential disk transfer rates of 1.5 gigabytes per second, as compared to the current 100 megabits per second,

— native hot swap capability so you can remove drives from an array using the arrays software, and

— new thinner and longer cables to connect the drives, rather than the current thick, ribbon like cables, which often prevent good airflow inside a computer cabinet.

Elizabeth M. Ferrarini She is a free-lance writer from Boston, Massachusetts.

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