John, Mario, and the rest of the gang, We also use Retrospect to backup several Macs and a couple of PCs, for a total of 9 computers. We've only had to restore the PCs so far *knock on wood* but it went rather well. Although we haven't been using Retrospect for very long, I'd like to add our answers to John's questions and address some issues brought up by Mario. [Only portions of the original messages are included to save space.] >John Altman writes: >>1) What sort of tape drive do you use for 15 Macs, and what is its capacity? >>2) Do you do incrementals or always full backups? >>3) Do you run into problems with slow networks, and the backups not >>actually finishing? >>4) Do you have a dedicated backup server, or do you use a machine >>that is in use everyday? (1) We use DVD-RAM.* Caveats: although double-sided DVD-RAM disks have a 5.2GB capacity, only 2.6GB (one side) is available at a time, making it necessary to physically flip the disk to access the second 2.6GB side. Currently, 5.2GB DVD-RAM disks cannot be read on DVD-ROM drives, but single-sided 2.6GB DVD-RAM disks can be converted to read-only disks that CAN be read on DVD-ROM drives. >(1) We use CD-R. Several reasons: it's much faster, it's much easier, >it's much cheaper, it's easier to store. ...or looking at it another way, tape drives are slower, require cleaning and special mounting/dismounting procedures, are more expensive (thousands of dollars for DDS or DLT drives), and tapes can be damaged by magnetic fields. The tapes themselves can only be used a limited number of times before they wear out, and are not suitable for long-term archives.** (2) We have 2 backup sets that alternate daily to incrementally backup the network. Full backups are performed monthly. (3) The only times I've had backups not finish were when the DVD-RAM disks needed to be changed after hours. Most likely there is a way to get around this, but I haven't found it yet. (We don't experience "slow network" performance during backups.) (4) We use our "administrative" Mac as our backup server. This is not usually a problem, since if the Mac is needed after hours I can (a) continue to work (slightly less efficiently) while the backup takes place in the background, (b) postpone the backup to take place later that evening, or (c) skip just that evening's backup. * Mario cautions against using DVD-RW (DVD-RAM) for backups. >I would NOT go with CD-RW (or DVD-RW, if it's available), >because (1) the cost is much greater, and (2) the idea of backups is that >they are permanent! DVD-RAM disks ($52.99 for a 5.2GB disk) are about 4-times more expensive per MB than $1.50 650MB CD-r disks. We use them primarily as an means to restore a computer in cases of emergency, and also as a short-term data backup. Long-term data archival is done on CD-r. Basically, we are using DVD-RAM because it is available and allows more flexibility in CD-r layout. (I suppose the efficiency of writing the CD-r at once instead of in sessions isn't that great of a benefit, but it makes me feel better.) :) Our backups are temporary, but our archive, which includes FCS files, is permanent. ** Our experience with the old 1600bpi reel-to-reel tapes leads me to distrust tape. Some tapes in our archive would fail to read back shortly after being written, and most tapes had failures after 5 years, sometimes preventing access to all files on the tape. When music CDs became popular in the '80s, recording companies wanted to re-release music on CD that was mastered on tape in the 60's and 70's and originally released on vinyl albums. Even though the master tapes were carefully stored for many years, some were completely useless. Because of the way tape is wound up on a reel, each layer of tape touches another. This made possible the transfer of magnetism from one layer of tape to another, i.e., one layer of tape could "write" a faint copy of itself on its neighbor layer. During playback of these master tapes, the faint "ghost" recordings were heard that were difficult if not impossible to remove during re-mastering. Eric /\/\/\_ Eric Van Buren, aa9080@wayne.edu \ \ \ Karmanos Cancer Institute and Immunology & Microbiology \_^_/ Wayne State University, Detroit, Michigan, USA
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