I was asked today if I thought that a disk-based backup system could do restores faster than a tape-based system. Mybest answer was a 'maybe', because it really depends on what thelimiting factor is in your restores. Let's look at all of the thingsthat have to happen in a restore:

1. you find and load the tape into the tape drive or tape library,if it's not already there.
2. if you have a tape library, it loads the tape into the

One of the slightly subtle advantages of disk-based backup systems over tape-based backup systems is thatcapacity expansion is much easier; all you have to do is start usingbigger disks. Since SATA is SATA, you don't need to replace yourenclosure, and it is relatively easy to have multiple generations ofdisks with different capacities cycling through your system.

Contrast this with tape backups. To upgrade to higher capacity tapes,you have to not just buy the tapes, you generally have to buy an entire

Our solution to the tape backup cost problem hasbeen to move to a disk-based backup system. The most important enablingthing for this is that when we built the latest version of our iSCSIbackends , we discovered that we could geta pretty nice 12-bay ESATA-based enclosure for reasonably cheap, and iteven has 'tray-less' drive bays that could be hotswapped.

(Tray-less drive bays are drive bays where you simply slide the baredrives in and out; you do not