Hard Drives Instead of Tapes? 70 TB Backup RAID at the University of Tübingen

Backup Management: Slick With Software

Once all the individual nodes have been connected via Gigabit Ethernet, there's still the question of how the backup process actually works - don't forget, there's no controller or server at all. The software solution to manage the backup was designed by the University of Tübingen; a program, operating as a server, is installed on any of the computers in the center. The client side of the software is then installed on all the other computers that need to back up data. The client contacts the server side of the backup program and initiates the backup as specified.

The administrator retains control over the entire data stock and can determine which data is stored on a particular module of the backup system. Adding or removing a module is as easy as moving the data to an outside facility.

The Real World: Hard Times For Tape Backups

There's one aspect in which Dr. Koch's backup system can't keep up with tape solutions: storing the backup medium in another location after the backup has been completed.

As long as this isn't necessary, Dr. Koch's backup system offers some rather unique advantages. For example, tape solutions often entail a great deal of effort: streamer tapes are an endless headache. Dr. Dilling has even had drives break because the computer center was using tapes from different manufacturers. Of course, tapes being folded over when the robot changes the media is just a minor problem, relatively speaking. Then there's the fact that you need an experienced administrator at the ready 24/7 - at night, when the backups are performed, and during the day, in case a backup needs to be available chop-chop. Since delays are the bugaboo of a backup system, you probably won't be able to get away with just having the administrators on call, leading to staffing costs that we don't need to get into.

There are also some very banal issues with streamer systems that even non-experts can easily follow: for one, a backup system has a limited number of streamers. If they're all in use when a request comes in for a backed-up data record, you either have to wait a tortuous eternity to have the data restored (and a watched pot never boils fast enough, it seems) or you have to interrupt an ongoing backup. Not to mention the time needed to switch tapes and fast-forward to the proper spot in the tape.

Other chinks in the armor are the backup server - basically the control unit for tape-backup systems - and the robots themselves. If any of them break down, you're out of luck. In an IDE system, you can immediately sever a defective node from the backup system and deal with it on its own.