SCSI error when running L&TT on an StorageWorks autoloader.

[Jens Erik Hegstad]

When I run an L&TT test on an StorageWorks 1/8 Autoloader with an Ultrium 960 drive. I got these SCSI errors:

The current SCSI configuration is likely to be limiting the performance of the drive.
|__ Please check that your HBA is the correct type for the drive and that the cabling is good.
|__ The SCSI configuration referenced is the one for which device analysis was run and/or the support ticket was pulled.
|__ If this is not via your backup server then you may not have an issue.
|__ The drives hardware compression algorithm is currently switched off.
|__ This was probably set by the backup software.
|__ The drive's setup has not been altered.
|__ Current SCSI transfer rate limited to: 160 MB/sec. Recommended: 320 MB/sec. or better

Anyone has any idea about what’s wrong ?

[Torsten.]

I guess it's exactly what the tool is telling you:

"Current SCSI transfer rate limited to: 160 MB/sec. Recommended: 320 MB/sec. or better"

Your servers SCSI card seems to be too slow.

[Jens Erik Hegstad]

I'm using an HP Single Channel Ultra320 SCSI HBA G2 card.

[Alexander M. Ermes]

Hi there.
One or two ideas.
Did you check the SCSI interface bios config ?
Switch the hardware compression on the drive to ON ( either by hardware or by software ).
Rgds
Alexander M. Ermes

[Jens Erik Hegstad]

Do you know how to change compression by software ?

[Torsten.]

This depends on the software.
If you are using windows, you can go to the device manager, locate your drive, open the drive properties page and click the config tab. Here you can enable/disable the compression.
But how about the scsi connection? Is the lib the only device on your SCSI controller?

[Jens Erik Hegstad]

There are no config tab on the driver, maybe because i use an Veritas driver as recomended by BackupExec installation.

There are also an Event error in the system log. Event ID 11, The driver detected a controller error on \Device\Scsi\Symmpi1.

[Jaclyn Rothe]

1)Recommended HBA for LTO drives 39320 or ultra 320 card. Continuing to use this restricing scsi controller will limit many things including compression as well as throughput. Also, this could damage your drive and warranty.
See: http://www.hp.com/products1/storage/compatibility/tapebackup/ThirdParty/index.html

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&objectID=lpg50063

2)Algorithm... HP tape drives have self compression. They typcially get 2:1 compression and I have seen 2.5:1 compression occassionally. Veritas Back Up Exec most often disables our drives algorithm in regards to compression. This happens when your back up software has a setting for compression. Compression should be 'un-selected'... no setting made in back up software, for this algorithm to prevent being disabled and for you to get the best compression ratios. Typically I have seen software get 1:1 to 1.7:1 compression.
My suggestion is to turn off your compression setting in your back up software... and run the test again to see if the algorithm is still turned off. Sometimes LTT will detect this and ask if you want to re-enable this now. If this does not recover the algorithm, you might have to flash the firmware to get this recovered so the algorithm will work again.

3)Ignore: "If this is not via your backup server then you may not have an issue.", if you are testing this unit from the local computer.

[Jaclyn Rothe]

Please attach the support ticket so I can see the settings. You can find the saved support tickets from LTT in File... load support ticket.
If you have anything else on the scsi bus this will limit the LTO transfer rate.
Ultrium units will automatically slow themselves to match the slowest unit on the scsi bus... so separate scsi controllers for each scsi unit is always recommended.
However, this might have been changed in the scsi bios. Check on post for your scsi bios prompt. Check if there is a way to "change/view host bus adapter settings"... then change the sync transfer rate on the card's ID (default #7) and the device's ID to 320 (that is 320 mb/s).

[Curtis Ballard]

Please ignore all the comments about compression. This statement refers only the the negotiated transfer rate on your SCSI bus.

The HBA you are using is fine.

While the recommendation is 320 MB/sec I wouldn't be too concerned about a negotiated rate of 160MB/sec since that is unlikely to impact your performance. At 2:1 compression the drive runs at 160MB/sec. If you get better than 2:1 you will lose a little performance but most hosts can't actually drive that speed.

There are a few possibilities for why your system hasn't negotiated for 320 MB/sec.
- Bus length/capacitance/other is causing errors at 320 MB/sec so the HBA automatically dropped back to 160MB/sec
- The HBA driver is old. There was a driver update several months ago to fix a negotiation issue that occured in some specific configurations.
- You might have encountered a corner case where the negotiations didn't complete correctly. A firmware roll will be available in the near future to correct that issue.