Arcserve, DLT Library, Single DLT, config issue via SCSI

[mcse924]

I have an Arcserve running on a W2K HP-Compaq DL380 server with Overland LXB dual 8000 drive library setup and have attached a new single 40/80 DLT drive to the end of the SCSI chain. This was simple enough, but I noticed a degradation in backup performance. This is the current SCSI ID configuration:

7 = SCSI Controller (default setting)
6 = Overland Library (default)
5 = Lib Drive 2 (default)
4 = Lib Drive 1 (default)
3 = Single DLT (daisy chained)
Terminator on single DLT drive - end of chain

I am by no means a SCSI or Arcserve guru, so I did not expect any impact on my backup jobs. Is my SCSI configuration above the most efficient? Should I make the single DLT drive SCSI ID# 8 instead of 3? Should I rearrange the other id's? Should I rearrange my cabling? Right now, it's conroller-library-single dlt, should I change to controller-single dlt-library? I read in the single DLT manual that an id above 6 (the factory default) is NOT recommended, but it did not say why. Any feedback would be appreciated.

Carpe diem, procrastination is the thief of time...

 

[Cyklops]

What SCSI controller are you using ?.What was your former SCSI configuration ( or was this the initial setup )
As you are using just one controller all data transmission goes over the same bus so, depending on the controller type, it is possible that the SCSI bus is becoming the bottleneck in the whole backup configuration here.

regards

 

[davidmichel]

Two of those drives per contoller is the limit before you can expect a loss of performance.

 

[mcse924]

The SCSI card is an Adaptec 29160 Ultra 160. The SCSI card is for the DLT hardware. There is an on-board SCSI for the SCSI hard drives.

The above is the original configuration, with a single DLT added. Im confused as to why this would cause a bottleneck. I only added the single DLT so I could perform quick restores with it, instead of the library. The single DLT is not used most of the time. The two library drives perform their duties simultaneously (nightly jobs). The three drives will NEVER be used simultaneously. I may just remove the single drive to avoid problems.

I'm just amazed at how INEFFICIENT this setup is. So much for being able to daisy chain 15 devices, what a crock.

Carpe diem, procrastination is the thief of time...

 

[davidmichel]

If the third drive is causing the problem without being used then the problem could be cable related. There is a 12 meter length limitation for the SCSI bus. That is from the SCSI controller to the library in port, from the library in port to drive one, from drive one to drive two, from drive two to the out port, and then from the out port to the stand alone tape drive. That total length is to be less than 12 meters. It also could be related to the type of cable used to attach the stand alone drive, or just a problem with that cable.

 

[spi200]

Hi

Check the termination's - You should only have One Term. on the end of the cable ie after your DLT and One on the Card internal.
DLT's can have Auto termination set (Switch 5) I think, but carn't quite remember. Have a look at your manual or download one from the NET like I did.

Regards

David