Small server backup options


In a centralized IT department, backup isn't a question, it's a requirement.

But what about the remote location that has a Windows NT Server with 10 to 30 people using it for file storage and print services? Who's backing up that box? If you've got a big enough pipe on your virtual private network (VPN), the backup can still be the responsibility of the central IT department. But what if the VPN connection is slow, or doesn't exist at all?

Magnetic tape is still the most cost-effective solution to remote location backup. But what format, and what speed tape? Go top-notch with a DLT? Go slow and inexpensive with a DAT? Or a QIC or TRAVAN drive? All will work. Recently, however, I was given the opportunity to try a new tape drive that has some interesting technology.

OnStream, a Longmont, Colo. company, has been quietly -- almost too quietly! -- building a product line that offers speed, capacity and cost-effectiveness. The technology involved has something old and something new.

The old aspect of the drive is its use of an eight-bit wide read/write head. Older so-called nine track drives did this for years. There's nothing really interesting about this point, except that most PC and PC server tape drives don't work like this anymore -- they use a helical scan technology that makes the effective head-to-tape speed much higher than the actual tape motion, and use a single-bit read/write head.

The new aspect is the fact that the drive uses (1) a servo track recorded on the tape to ensure that the head is precisely positioned over the tracks and (2) a variable- speed motor that adjusts the speed of the tape to the speed of the system delivering data. This is decidedly different from other tapes; the speed of those is usually fixed, and the tape must stop, rewind, and restart if the computer can't feed data quickly enough.

I contacted OnStream to get an evaluation unit. My goal was to compare the OnStream SC30e to a Quantum DLT 4000. Since I already had a Quantum with a fast, narrow SCSI interface, I selected the OnStream that most closely matched the specs of the DLT.

First, the differences. The DLT uses a semimanual load -- you lift a handle, put the tape in, and lower the handle. The drive takes over from there. The OnStream has a button that opens the door and allows a tape to be inserted. As soon as you insert the tape, the drive swallows it and the door closes. The DLT has a button with which you can override the tape density and force hardware compression; the OnStream does not. The DLT has hardware compression built in. The OnStream model I used does not (compression is performed by the backup software), but newer models do. The DLT has a capacity of 20 GB native and 40 GB compressed. The OnStream has a 15/30 GB capacity. The DLT IIIXT cartridges have a Web price of $37 to $40. The 15/30 GB ADR cartridges used by the OnStream drive cost about $34, slightly less per tape for a three-pack.

Both drives were attached to an old ISA SCSI device. I regret this because I think both drives suffered because of the limitations of the ISA bus. Both drives performed at about the same speed: roughly 60 MB per minute. Previously, I had used a Quantum DLT 7000 on this same system, but it had a Fast/Wide SCSI interface. Speeds of 130 to 160 MB per minute were not uncommon on that drive. When the DLT and the OnStream both showed about the same speed -- a speed that was only half the specification for the OnStream -- I suspected the SCSI adapter (or the ISA bus) was the culprit. I have been waiting for an AHA2940 PCI narrow SCSI card from Adaptec, but it didn't arrive in time for this column. I'll provide a quick update if (when?) it does.

Of course, an orphaned tape drive is less than desirable, so the strength of the manufacturer is important. While OnStream is privately held, its CEO is the founder of Colorado Memory Systems (he sold that company to Hewlett-Packard) and its list of investors is impressive. Because OnStream is not a publicly traded company, its financial information is not published.

Since this column is intended to address departmental server backup, I didn't take the time to use the software that comes with the drive that would be of more interest to individual users. The Echo software includes the ability to use the tape drive as if it were a disk, using a drive letter and copying files to the tape. It can also be set up to automatically copy each file that is updated to the tape drive in a background process, providing a continuous backup. I wouldn't recommend this for a server, but I could see how it would be beneficial in some environments.

Final result: the OnStream SC30e performed on my system with same speed and reliability as a Quantum DLT 4000. The SC30e has a street price of under $500; the Quantum DLT 4000 goes for over $1500. While one can never predict the future viability of a high-tech company, I'd feel comfortable using the OnStream as my only tape drive.

Now that I feel I've covered the background for storage, we can move onto the more fun stuff. I'll come back to backup hardware and software as needed to provide updates to this critical issue, though.

Next week: in the past 10 years, CPU's have gone from 20 MHz to 1 GHz. Over the same period of time, disk drives have about doubled in speed. Can disk drives be made faster without their prices going through the roof?

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