StorageWorks DAT40 on SCSI bus where there is a disk

[Franco A. Sicoli]

Hi.

I am just reading the "Before you start" notes on the "Getting started guide" that came with the HP StorageWorks DAT 40 tape drive (C5687C).

It states: "Do not attach the drive to the same SCSI bus as a your disk drive".

I wonder if it is just a performance optimization suggestion or a must.

I have no other possibility but to add the DAT to the same an ONLY external SCSI bus where there already is a SUN ultraSCSI DISK.

Here is (part of) the output from ioscan -f:

ext_bus 0 0/0/1/0 c720 CLAIMED INTERFACE SCSI C896 Fast Wide LVD
target 6 0/0/1/0.3 tgt NO_HW DEVICE
tape 0 0/0/1/0.3.0 stape NO_HW DEVICE HP C5683A
target 7 0/0/1/0.4 tgt CLAIMED DEVICE
disk 2 0/0/1/0.4.0 sdisk CLAIMED DEVICE SEAGATE ST318203LSUN18G
target 0 0/0/1/0.7 tgt CLAIMED DEVICE
ctl 0 0/0/1/0.7.0 sctl CLAIMED DEVICE Initiator
ext_bus 1 0/0/1/1 c720 CLAIMED INTERFACE SCSI C896 Ultra Wide Single-Ended
target 1 0/0/1/1.2 tgt CLAIMED DEVICE
disk 0 0/0/1/1.2.0 sdisk CLAIMED DEVICE SEAGATE ST318404LC
target 2 0/0/1/1.7 tgt CLAIMED DEVICE
ctl 1 0/0/1/1.7.0 sctl CLAIMED DEVICE Initiator
ext_bus 2 0/0/2/0 c720 CLAIMED INTERFACE SCSI C875 Ultra Wide Single-Ended
target 3 0/0/2/0.7 tgt CLAIMED DEVICE
ctl 2 0/0/2/0.7.0 sctl CLAIMED DEVICE Initiator
ext_bus 3 0/0/2/1 c720 CLAIMED INTERFACE SCSI C875 Ultra Wide Single-Ended
target 4 0/0/2/1.2 tgt CLAIMED DEVICE
disk 1 0/0/2/1.2.0 sdisk CLAIMED DEVICE HP DVD-ROM 305
target 5 0/0/2/1.7 tgt CLAIMED DEVICE
ctl 3 0/0/2/1.7.0 sctl CLAIMED DEVICE Initiator



After some experiments I was able to add and see the tape alone, and the disk alone, but not together (ioscan output). I figured out the problem in the wrong cable I was given to connect the two devices, but before requesting the purchase of the correct LDV/SE HD68M/M cable (C2978B) I want to be sure that the two devices can co-exist.

Thank you in advance for answers.

Franco Sicoli

[Claudio Ruzza_1]

I experienced myself a connection of a disk and a tape in the same bus. Different environment, different OS (Solaris), different disk and tape drive, but I believe that my experience can be valid anywhere.
No problem for Solaris to see the devices. Problems arises when accessing in the same time disk and tape: Write operation to disk and/or tape drive suddenly fail, generating strange error messages. Tried for a month, never been able to complete a backup job of less than 5 GB.
My conclusion is that this recomendation is not for performance issue.
It's a must if you want to make your system reliable.

Claudio