Wildly varying (and low) backup rate to disk and different tape hardware

[Dominic_Moore]

Hi,

I installed a new Exabyte VXA320 packetloader library a couple of days ago expecting it to give me about double the rate of my older VXA2 packetloader. I ran a test backup to tape of around 42GB data and it reported backing up around 25GB at 778MB/min in around 30 minutes.

Subsequently I set up my overnight backups to use the new library and one job ran with a rate of exactly 100MB/min and took seven hours! A backup to disk ran at 227Mb/min. Previous overnight backups had run at 800-900MB/min on the old library and the disk but had also randomly dropped to the 100-200MB/min range some days.

I ran the exact same test backup to the tape library again this morning and it ran (until I canceled it) at 99MB/min.

What can be the reason for the x8 variation in speed on the same data? Thre are no logged errors anywhere that I can see.

TIA

[Patty_McGowan]

Dominic,

Drivers and Firware. Also here is a bit out of technote 231488:

How to potentially improve tape backup performance:

1. Make sure your tape drive is properly defined for the host system. It is common for a SCSI host to disable the adaptive cache on the drive if it doesn't recognize the product identification string returned by an inquiry command. This cache enables features like drive streaming to operate at peak performance. See your product manual for more details on this.

2. Put the tape drive on a non-Raid controller by itself

3. Make sure that the settings are correct in the controller's Post Bios Setup Utility

4. Make sure that the proper driver/Bios update for the SCSI Controller have been applied

5. Confirm that the proper cabling/termination for the devices are being used

6. Update the firmware on the tape drive to the latest level. In some rare cases, the firmware may actually need to be downgraded to improve performance.

7. Check the Preferred Configuration Settings for the tape drive and verify that they are set properly

8. Check the tape drive and tape media statistics to see if errors occur when backups run. If excessive errors show, the SCSI Controller Bios Settings, the Device Drivers, the Bios/Firmware Level, or the type of tape media being used may be incorrect for the tape device.

9. Run erase jobs on tapes and replace tape media as per the manufacturer's recommendations

10. Check the Windows NT or Windows 2000 System and Application Event Logs for warnings/errors. Event IDs 7, 9, 11, and 15 in the System Event Log usually indicate that there is a hardware problem.

More information is can be found at:

http://support.veritas.com/docs/231488

Patty

[Dominic_Moore]

Hi,

Thanks for the rapid response. I will try the suggestions of course where possible, but there are two different tape drives and a disk here, as well as the exact same job being eight times slower on the same hardware with no changes made. The driver/firmware is not varying between jobs and is different in each hardware instance.

Thanks