Exabyte VXA-2 Tape Backup System
By Joel Shore
May 3, 2003
without saying: If you are a network administrator, you’ve
already developed a comprehensive plan for backing up the data
on your servers. Right? If you haven’t done this yet, put it on
your calendar for today—not tomorrow, today. Today!
One thing we
all know is that disk-storage prices have dropped like a rock
even as capacity has skyrocketed. Like moving into a bigger
house, these giant disk drives have
more room for more stuff. That means more files to back up.
And that means using tape drives. Big tape drives.
As the years
passed and the need for high-capacity tape storage grew, various
technologies have come and gone. The alphabet soup of these
technologies, QIC, DLT, DDS, and others have given way, at
Exabyte, to VXA. The format clearly is a winner: Apple, Compaq, Fujitsu,
IBM, Logitech, and Toshiba have all signed on. Expect more to
DDS-4 tape drives, among the most common in use today, just can’t compete anymore. The maximum
capacity of a DDS-4 tape drive, with data compression, is only
40GB, a mere pittance by today’s standards. After all, you can
buy an entire computer, complete with 80GB-drive, for less than
$1,000. VXA-2 drives are
huge in comparison—they hold four times as much. With
compression, you’ll fit up to 160GB of data per cartridge.
only does VXA-2 boost capacity by a factor of four, it’s also
twice as fast as DDS-4. Combine that with hardware that’s less
finicky, and you wind up with, well, bigger, faster, and more
reliable. That’s a darn compelling argument.
VXA-2 Tape Usage Guide
*With 2:1 data compression
make matters even worse for intrepid DDS users, the
manufacturers of tape drives have chosen to abandon DDS
altogether; DDS-5 will never see the light of day. That makes
the DDS format a lame
duck. Thinking of migrating from an old, slow, small DDS-4 drive? Think
I took a look
at Exabyte’s external VXA-2 tape drive, which provides 160GB of
data storage through a low-voltage differential (LVD) SCSI
connection on a single tape cartridge. If your backup needs are
greater, VXA-2 is also available in either 7-tape or 10-tape multicartridge
autoloaders. You can get capacity up to a whopping
1.98TB (that’s terabytes, nearly two trillion bytes!). Exabyte
also manufacturers a VXA-2 drive with a FireWire interface.
Packets and variable speed make VXA different from other tape
technologies. Older technologies recorded by placing data
in a continuous stream, parallel to the edges of the tape.
Called linear recording, it’s very similar to the way audio
cassette tapes work. Linear recording eventually gave way to the
more-modern helical-scan recording scheme in which a spinning
recording head laid down tightly packed data tracks at an angle
to the tape’s edges, just like the VCR sitting next to your TV.
Like linear recording, helical-scan recording looks at the data as a continuous stream.
those long data streams (a large file, for example) and splits
them into small chunks, called packets. It’s very similar to the
way your network breaks down a large file into packets for
transmission over the Internet. As each packet is written to the
tape, it is verified for integrity. The intent is to ensure
Also unique to
VXA is VSO, Variable Speed Operation.
VSO enables VXA drives to adjust
the tape speed to match the data-transfer rate of the computer
furnishing the data. How cool is that? This on-the-fly speed adjustment enables VXA to eliminate productivity-reducing back-and-forth tape
movement (“backhitching”) and wear and tear (on both the tape
and the drive). The aim, again, is better performance, greater
reliability, and absolute data integrity.
Setting up a VXA-2 drive is rather straightforward. First,
you’ll need a SCSI adapter installed in the host computer or
server. The drive does not include a data cable, so be sure to
have a Wide LVD, 68-pin cable on hand. The external version of
the drive includes a terminator, the internal version does not.
As with any
SCSI device, you first set the SCSI ID by pressing the “+” or
“—” tabs on the SCSI ID switch. Next, you connect the SCSI cable
from the computer to either of the SCSI ports on the tape
drive’s rear panel. If you have several SCSI device connected in
the chain, and the drive is the last one in the chain, install
the terminator on the unused port. Finally, connect the power
power up the drive, its four LED indicators flash in sequence,
letting you know that it is doing a self-test.
When this diagnostic routine is completed, the power indicator
LED illuminates in solid green. Next, you load a tape and wait
for the tape indicator to light up in solid green. The drive is
now ready for use.
can make backups, you’ll need to configure your backup software
to recognize the presence of the VXA-2 drive. Once this is done,
be sure to run a small backup and restore test to make
sure everything is configured and working properly. After you’re
satisfied with the test, you can place the drive in service.
Why run a complete
backup-and-restore test? Simple. No one really cares if a drive
can record data. It’s
retrieving it that counts!
tape drive is
fast, reliable, and offers oodles of capacity on a single tape
For new installations, it’s a great way to go. And when the time
comes to retire your DDS-based drives, VXA-2 is hard to beat. <