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Re: SCSI Domain Validation problems with LTO-4 drive and several SCSI HBAs

 
RalfG
Frequent Advisor

Re: SCSI Domain Validation problems with LTO-4 drive and several SCSI HBAs

The lib has two LTO-4 drives (as written in my first post) and the server has two SCSI HBAs.

I'm seeing this behaviour with both drives. One drive is exclusively connect to one HBA, the other drive + the lib with the second HBA. The terminators and cabels are connected to the rear of the lib.

This is described here (pages 2-12 to 2-15):
http://support.overlandstorage.com/jive/servlet/KbServlet/download/3518-102-1144/104248-105_A.pdf

The problem is not the cabeling or the termination. If I take the cable and connect an external Ultrium 1840 drive (firmware B22D) with the HBA everything is ok.

Maybe it's the old fw, or something with the lib's backplane.
Curtis Ballard
Honored Contributor

Re: SCSI Domain Validation problems with LTO-4 drive and several SCSI HBAs

I agree that changing the cables is unlikely to solve your problem as your other drive won't negotiate to U320 however the cable diagram as shown in figure 2-10 of the Overland manual is incorrect and if you were to be able to get the system running at U320 speeds you would have problems with that drive. The terminator needs to be on the drive not on the library controller.

It is possible for the library firmware to tell the drive to never negotitate to U320 if the library supports that function. I can't say about the Neo but it may have restricted the drive to a slower speed.

You could try their suggestion of disabling domain validation to see if it is ever possible to get the drive to negotiate to U320 however I agree with you that if domain validation is forcing the drive to a slower speed then running at U320 is likely to have problems so that wouldn't be a solution, just a test.
RalfG
Frequent Advisor

Re: SCSI Domain Validation problems with LTO-4 drive and several SCSI HBAs

I had contact to the LSI linux driver developer. He was very clear on disabeling DV:

| That make no sense. The devices will net 5
| MB transfer speeds if you don't do DV.

With the LSI linux driver, it's not possible to diable DV.

After the ext. drive was able to do U320 with the LSI HBA, I'll now wait what Overland will tell me next week. The frustrating thing is that they used ltt for some basic tests and got ~130 MB/s. They then claimed that U320 wouldn't be needed because the drives couldn't do more. I got no answer if their drive/lib was correctly working in U320 mode (in 5 weeks!).

Curtis Ballard
Honored Contributor

Re: SCSI Domain Validation problems with LTO-4 drive and several SCSI HBAs

Thanks for the info from LSI. It sounds like their HBA defaults to the lowest transfer rate if domain validation isn't run which is backwards from the cards I have played with where not running DV causes the card to always attempt the highest possible speed.

You already know that the drive can run faster then 160 from your own tests so no sense even addressing that point.