Just some comments from my own experiences with backup at Network Appliance:
On 04/22/98 08:57:07 you wrote:
| Do you use ndmp?
No. Although things have gotten better, directly attaching any device with a robotic arm to a filer is not going to end in a pleasant way. If the stacker hangs (as some do), you need to power-cycle the filer and the stacker. This means downtime. I would rather reboot a dedicated unix box that does backups (and will not interfere with anything).
I can say that having used several DLT-4700 stackers attached to several filers over the years, I NEVER had one of those stackers hang. So I would have to say that this is pretty rare for the DLT-4700. If you use another stacker, I suppose it could be more of a problem.
I did have some DLT-4000s fail, but nothing like an intermittent hang to be cleared via power-cycle; they busted completely, requiring them to be returned. It IS true that if your dump device goes out to lunch during a dump, and you started that dump via, say, rsh, you will have to reboot the filer to kill that dump session (otherwise you could ctrl-C). There was some talk of a dump abort command being done, and/or the notion that one might be able to use ndmp to kill that old session, but I don't know if either are possible with the latest software. However, rebooting was sufficient (no power cycle needed for the filer) to clear the session, and that usually takes less than 5 minutes, so downtime wasn't much of an issue either in those cases.
For us, it was cheaper to have that directly attached device than to spend money on increased network infrastructure for network like dedicated gigabit, the dedicated UNIX server, the software, etc. For someone with different requirements, network backup might be the better way to go; it certainly scales better in the long run if you can set it up properly to start with.
| How many streams of backup do you use in parallel?
I can only do 1 (only 1 drive). My friend does 4... He also does something called vaulting. After a level0 is done, the software then duplicates the tapes and spits them out. Thus he sends the copies off site and can restore more effectively in case of an emergency (no delay in getting tapes back).
This software duplication sounds very cool... actually, something that did it in hardware would be even cooler. Allowing you to keep on copy on-site is a very nice idea. I'll have to try that in my next backup plan.
| What speed/rate do you backup (GB/Hr) per drive?
Slow. 3-4GB/hr. My goal is to increase than an order of magnitude. I would like to be able to restore 50GB in less than 1 hour. AIT looks like the quickest (and least expensive) way of accomplishing this.
A word of caution here... I doubt changing your tape drive is going to increase your backup or restore times if you continue to do it via rsh dump/restore over the network, given the limitations of the software. Things may have improved with the more recent release, but my advice would be to either use local tape or use NDMP over the network if you want to get better performance. amd stick with DLT.
To the original poster - Network Appliance can provide you with numbers for all of these things, and I can tell you that last year the numbers they were using were pretty authentic, having been put together from customers, in-house testing, and "real world" in-house testing (myself running the backups as an internal customer). I wouldn't have any reason to doubt the numbers they might give out today.
Bruce