Disk or tape: Is the debate finally over?

Which is a better solution when it comes to backing up and
archiving data? Disk or tape? Had you asked this question a few years ago,
people would have given you funny glares. But if you ask the question today,
then be prepared for a healthy debate on the subject. The fact is that backup
and archival was purely the realm of tape. Nobody even bothered to consider hard
drives for the job because they were ridiculously expensive. But the very fact
that disk has reached a stage where you can actually debate its usage over tape
is quite commendable.

It's pretty interesting to see how hard drives have
steadily encroached into the tape drives' domain over a span of just a few
years. Hard drive prices fell, capacities rose along with the throughput. Then
vendors started offering hard drive storage as an intermediary solution to
backup. So you would first back up your critical data to the disk before it
finally went to tape. The logic was that since the backup window on tape was
pretty long, it couldn't be used for instantly backing up large volumes of
data, such as that coming from an e-commerce site.

The growing popularity of disk doesn't mean that the world
of tape hasn't seen any action at all. The technology being used in tape
drives has been constantly improving. Today, you have tape drives that can back
up data up to 800 GB compressed. The speed has also gone up with capacity,
thereby reducing the backup window.

Several debating points emerge between disk and tape from
whatever we've said so far-capacity, cost, speed of backup and retrieval,
technology changes, and portability. When it comes to backing up huge volumes of
data, then the tape is far ahead of the disk. On the cost front also, disks just
can't match.

The last point on portability has mostly been in favor of the
tape. It's much easier to take a cartridge and stack it in a cupboard. You
couldn't imagine doing that with a disk. However, portability is now being
questioned in favor of disks. But with the concept of disaster-recovery sites
gaining ground, organizations can have exact replicas of their IT infrastructure
in remote locations. These can be backed up in near real time, and the disaster
recovery center can even take over should the primary center fail. This
eliminates all data-management issues. It may seem like a trivial issue to
retrieve data, but when you have terabytes of data backed up in hundreds of
tapes, it's not an easy job finding that one tape that has the data you're
looking for desperately. Likewise, the cost of logistics can also be pretty
high. Data archival, which involves putting away data was also something where
tapes were preferred. But even here, vendors have started offering disk-based
solutions.

Given all these points, the disk has come a long way and taken a fair share
of the tape backup market. But there are still lots of organizations that can't
afford remote disaster-recovery sites, and the higher acquisition costs of
disks. They still prefer tape and are willing to have longer backup and
retrieval windows. But if disk costs continue to fall, then we may be in for a
surprise.