On 04/23/98 08:31:55 you wrote:

Hi,

I wanted to check out the following issue that was brought up in one of the responses to my poll (still waiting for more replies):

When a TLU (tape Library Unit) is directly attached to a fileserver, does every reboot of the TLU necesarily mean you must reboot the fileserver?

No, it doesn't. At least with the TLUs I've used (Quantum DLT-4700, Breece Hill) a reboot of the filer was not necessary if the TLU was power-cycled. However, there was rarely any need the power cycle the TLU in the first place.

Note that you can't properly "hot swap" a tape device on an off a filer, but I have seen it work before, although that's not properly supported and probably depends a lot of the specific filer, tape device, OS, and the phase of the moon. :)

OR

Is this only specific to the TLU vendor ( as suggested below).

I think it's specific to that TLU vendor.

I see this as a serious issue!! I don't want the uptime of my fileserver to be affected by something like this.

Understandable. I don't think it's different from any other backup server in this regard.

| You mentioned a very interesting note - attaching a jukebox | to the fileserver might mean that you will need to reboot the file | server from time to time. WHY? | When you reboot the tape library juke box - does this force | you to reboot the file server as well?

If the stacker/jukebox hangs for whatever reason (robotic arm, etc), and you need to power-cycle the tape device, you cannot do so with the filer on. You run the risk of frying the scsi bus.

I find this difficult to believe, considering the SCSI bus has to deal with, for example, the power supply on shelf suddenly failing, or the power supply of the stacker itself, etc. If one considers the case of a short power outage, you can't control wheter the filer or the stacker will get power first when it comes back on, so sometimes the filer will be on first. Surely equipment is robust enough to support this.

Now, it could be that the problems I had were related to the specific DLT stacker (an ADIC vls library) we used. I don't know. I have not risked that sort of problem any more.

The risk, if there is one, would have to be very small. No more than the risk for any other incident relating to power, and the number of SCSI busses fried in those instances must be small. If you have a stacker that is hanging frequently, you're much better off worrying about fixing the stacker's hanging than the small chance of a SCSI bus being fried if you power-cycle.

See also my earlier comments about the filer possibly having to be rebooted if you can't abort a dump/restore that was in progress when the stacker hung. But that is a software issue, not a hardware problem.

Bruce