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.