On 04/22/98 11:15:20 you wrote:

Because if you have 8 filers, most, potentially all with > 20GB of compressed data, putting an autochanger on each filer is prohibitively expensive. Going the other route and putting, say, a DLT7000 on each filer is also nuts. Cost for one of those around here (toronto, ontario, canada) is something like $12500 plus the cost of a tape monkey to run around and change tapes daily.

While I agree that ultimately network backup is a cheaper and easier to manage alternative solution, I think you overstate the case against local backup. There are several key points that you need to be aware of in a network backup solution:

1. If you have a good (read - frequent) backup scheme, and your filers are large, you won't save on the number of DLTs you buy. Consider the case where those 8 filers all have to be backed up once/day, and it takes about a day to run the backup. You'll have to have just as many DLTs streaming away on that backup host as you would if each one was attached to it's own filer. Now, a more realistic example would probably allow you to cut the number of DLTs in half, but you will have to make sure your schedule everything properly. And can recover quickly if you have a failure.

2. You probably can't afford to saturate whatever network you already have, so you'll need a dedicated backup network. So gigabit is overkill, but once you factor in your 100mbit hubs, the possible need to buy additional network interfaces on your filer and the backup hosts to support this, not to mention the backup host itself, the cost differential is less than it first appeared.

3. You SHOULD have a tape monkey running around to change tapes daily. You don't want those tapes sitting there; you want them labeled and catalogged and shipped off-site. This doesn't change if you have a central backup solution, and at the very least you'll still have to change tapes just as often. Unless you get a library with a bigger tape capacity for your central server than you would for an individial stacker for each filer, which again is a price consideration.

4. You will incur a performance penalty, although with the more recent releases that penalty may be less than 10%.

So, IMHO, network backup is probably more expensive at 4 filers, cheaper but not worth the hassle at 6, and only becomes really preferable at, say, 8 filers. But these numbers all depend on how big your filers are and how frequently you want to do your backups.

Bruce