"Disk Sleep" status on qlogic scsi sbus card on a sparc station 20 (sparc32, 2.4.17)

I know sparc32 is not mantained any more, but I'm still posting in case this problem with give light to a problem that might apear on another arquitecture.

I'm running kernel 2.4.17 on a sparc station 20 (with 2 procesors) running splack -current.

I have a scsi qlogic sbus card on this box on with I attatch an scsi tape or a multipack storage with some 8 to 12 disks on it.

While I run diferent aplications (not at a time) that are some I/O intensive on the devices attatched to this qlogic card and I sometimes see some huge sleeps on the process that is working on them.

I cat'ed /proc/{PID}/status and I see "State: D (disk sleep)".

Sometimes the process goes on working, but not often. I also can't send this process to sleep nor I can kill them.

I have used tar to back up an filesystem to a DD3 tape, and have also used rsync from another host (On a 100Mb LAN) to a raid formed by the disks that are attatched to the controller.

BTW, this does *NOT* occur on an ultra1 box (which is sparc64) running the same kernel version, and with the same set of disk or the same tape with the same qlogic scsi sbus card.

What test could I run on this box to give some more information to you guys that would help to resolve this problem?

Or else, what could be that problem, and what could I do to solve it?

Thanks in advance.

Alvaro Figueroa