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Lots of scsi resets on tape drive

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Dan Newcombe
Advisor

Lots of scsi resets on tape drive

(hard trying to figure out a decent subject line!!!)

We have an HP rp5740, with a Surestore 2/40 tape library. It is hooked into a SCSI C1010 Ultra160 Wide LVD A6829-60001 card. The changer is at ID 0, the drives at 1 and 2, and one channel of the card on ID 7 on on ID 6 (changed because it was happening when they were both on ID 7.)

HP hooked the drive up when the machine was installed, and the cableing matches what is in the book.

What we are getting is at the end of this message. Whenever we try to do backups (using Omniback with HP DLT tapes - can't blame another vendor :) they fail after a little bit...sometimes it's right away, sometimes a few gigs. An I/O error is reported by omniback, but the /var/adm/syslog/syslog.log has the messages attached below.

I have checked and all the cables appear to be hooked up correctly and snug. I was looking for any other ideas to try before calling HP support on this issue.

Thanks for any input
7 REPLIES
Dan Newcombe
Advisor

Re: Lots of scsi resets on tape drive

Forgot to add, this does not happen only when the drive is in use. As soon as the system is rebooted, before I even log in, the errors are being generated. After that, if you access the tape drives it starts to spit the errors out again.
Vincent Farrugia
Honored Contributor

Re: Lots of scsi resets on tape drive

Hello,

From ioscan I can see 4 drives and 2 controllers, are you sure it is a 2/40? Should be 4/40.

Also, you have 2 drives daisy-chained on each bus. While this should work fine, the recommended configuration is to connect the drives to separate buses, total of 4 controllers in your case.

DLT8000 technology only run at Ultra-Wide SCSI, so your Ultra160 should be able to handle their speed (backward compatible to Ultra2).

For some reason it seems like your DLT8000 cannot stream data across from server to them and vice versa. It is finding bottlenekcs which forces him to reduce the speed of stream, something which a tape drive is never happy about. Hence the SCSI resets.

Have you tried attaching the controller to only 1 drive (instead of daisy-chained to 2)? If this works fine, then the drive is unhappy being daisy-chained.

Reply back with feedbakc please.

HTH,
Vince
Tape Drives RULE!!!
Dan Newcombe
Advisor

Re: Lots of scsi resets on tape drive

A couple answers before I start yanking cables.

Just the two drives but it does have 40 tape slots - hence the 2/40. I guess it's a 4/40 sans 2 drives.

The drives are hooked to the one controller, but one connection to each channel on the controller card. I guess it is to provide a redundant connection. In this case, 0m and 2m are the same drive, and 1m and 3m are the same drive. Would make more sense if it was on seperate SCSI controllers instead of just different channels on the same controller.

It is not just streaming data across the network. If I do a tar from the local machine to the drives, I get the same result. Yesterday, I got the messages a) after rebooting before doing anything with the tapes b) just having omniback telling the changer to load a tape.

Thanks for the input...off to yank wires and see what happens.
Vincent Farrugia
Honored Contributor
Solution

Re: Lots of scsi resets on tape drive

Hello,

Unfortunately, multi-initiation on tape drives are not supported.

Tape drives allow only ONE connection, not two. The other connector is meant for termination or daisy-chaining purposes.

So, since you have 2 controllers, just remove one connection from each drive, and put a terminator instead. That should solve your problems (you know why it is not supported! :-) ).

This way, you will have the drives on separate SCSI chains.

HTH,
Vince
Tape Drives RULE!!!
Vincent Fleming
Honored Contributor

Re: Lots of scsi resets on tape drive

It sounds to me like you are dual-initating the tape drives... (putting both HBAs on the same SCSI bus)

I've had problems attempting to dual-initiate tape units before, so I'll suggest that you not do that.

Run 2 cables from your server to the tape unit - one for each drive (as suggested above), properly terminate the busses, and try it again.

If you still experience the problem, then I would suspect a hardware problem of some sort.

Let us know how it works in the single-initiator configuration.

Good luck,

Vince
No matter where you go, there you are.
Dan Newcombe
Advisor

Re: Lots of scsi resets on tape drive

To quote Lando from Star Wars "It's not my fault." :)

That is the way HP installed it. Trusted them.

Off to be a Terminator :)
Dan Newcombe
Advisor

Re: Lots of scsi resets on tape drive

This was indeed the problem. The HP tech who did the install wired it up like the disk drives - a redundant connection back to a controller.

I had assumed that the HP had been setup correctly by HP, especially since during the install he called in to his support to ask how to properly wire it.

Once I followed the instructions on page 33 of the surestore manual, everything seems to be working just fine. Only other problem I had was the drive's changed during my rewiring - what was drive 1 is now drive 2, which threw me in omniback for a bit, since for loading it refers to the drive number, but writing refers to the devicefile.

Again, thanks for all the help.