Removing a SCSI DLT drive on line ???

[A. Clay Stephenson · Accepted solution]

I replaced tens of SCSI tape drives over the years without powering down and have never had a blown card. I would be reluctant to do it on a busy bus (e.g. if your DLT were on the same bus as active disk drives but since these drives are supposed to be on a dedicated bus that shouldn't be a problem). I would power down the external drive and if this is the only device on the bus, I wouldn't bother to terminate it. Opening the bus will immediately trigger a SCSI bus reset but this is considered a normal (if unusual) SCSI event and the underlying protocol is designed to handle it.

The "safe" answer is , of course, power down all components but the "real world" answer is that that would make long uptimes very difficult. Your point about the controller being self-terminating misses the mark. The controller can supply one termination but the bus requires exactly two terminations but if there is nothing else on the bus, it really doesn't matter. As part of the replacement routine, you should do an ioscan anyway to make sure that the new device is "visible".

Operations like this really point out the importance of having a "sandbox" so that you could try out your questionable procedures without risk of clobbering something important.

[Sanjay_6]

Hi Mike,

I would not suggest you to remove the drive online. You can probably do this without affecting the system, but if in case a scsi reset goes into the bus then you'll be left with a hung system.

However if the drive is a hot plug one, you can remove it. We have some hot pluggable DLTs that we have removed without any problem. Just power it off and plus it out. Replace with a new one, wait for a few seconds and power it on.

Hope this helps.

Regds

[Mike Roger]

Thanks to all for the valuable replies were it shows lots of experience

[Ted Buis]

You should mention if the tape drive is connected to a core I/O SCSI connector or a PCI card in the card cage of the rp7400, and whether you are running HP-UX 11.0 or 11i. Go to www.docs.hp.com and search on OLAR if you have the drive connected to a PCI card as opposed to the core I/O.

[Ameet_HP]

I have done it too many times. DLT Drives are having seprate Power connection. Without stopping backup or powering off DLT Library, we have replaced failed drives or tape stuck drives etc. Also, this all work is done by HP itself. From business side, I will say, it does not cause anything to backup or DLT Tape Library.

Thanks,
Ameet