How to build a scalable backup solution

Many IT professionals see backup solutions as a necessary evil, like buying insurance. You hope you'll never have to use it, and if you don't, you may think of the money you spend on it as wasted. But you don't dare go without it.

Your backup solution doesn't save you from a dire fate every day like a firewall. It doesn't provide a dramatic improvement in performance or user productivity. It's just there until you need it. Then it's priceless.

From disk to tape
When your business is small, the easiest (and least expensive) way to back up your data may be to use a program such as Second Copy to run in the background and make a copy of your data files to another location, such as another server on the network. Because the backup of the data is on disk, it's fast and easy to retrieve it.

As the organisation grows and begins to accumulate more and more data, it's common to switch to a tape backup solution. The low cost of tape, as well as the ease with which it can be stored off-site to guard against having the backup destroyed along with the originals in case of a natural disaster, make it an attractive option. You can get autoloaders that do away with the need to manually insert tape cartridges into individual tape drives.

The problem is that tape drives, especially of the standalone variety, become more and more inefficient once you surpass a certain amount of data. Robotic tape library systems can be a solution, but they're costly (often tens of thousands of dollars). What's the difference between an autoloader and a robotic library? The autoloader contains one tape drive and multiple slots for tape cartridges (typically 10 or fewer). A library system encompasses multiple drives and a number of locations for cartridges.

And back to disk
While tape has been the backup medium of choice for large organisations for years, a recent trend as the organisation grows bigger still is to return to disk-based backup, but with a difference. Disk-based backup solutions for the enterprise are far more sophisticated than the simple scheduled copying programs used by smaller businesses, but they can also be costly.

One advantage of disk over tape is speed of access. You have to search through a tape from the beginning to find a particular block of data , while the heads on a disk drive can go directly to a particular place on the disk.

Disks also tend to be more reliable than tape. Most users of tape backups have had the experience of a backup or recovery failure; some estimates put the failure rate at 20 percent or more. Even worse, you often don't know that a backup has failed, or partially failed, until you need it.

The move from tape back to disk is based in part on the falling prices for high capacity hard disks, and in part on the difficulty of managing and rotating the large number of tapes required in the enterprise environment.