I have been upgrading our backup infrastructure here and ran into a snag.
Current setup:
8way 2.6ghz Xeon
32gigs RAM
Dual Intel 1000 ethernet
ATTO ipBridge 1500D (scsi -> iscsi adapter)
HP Ultrium 920 tape drive (destination drive)
DS3200 SAS unit (source drive with read and write cache enabled)
On Friday I tested this setup and the throughput was terrible, only around 370MB/min. I did notice that Single Block Write Mode was turned on for the tape drive, so I disabled this and the throughput shot up to 2200MB/min which is where it's supposed to be.
The problem I'm having is, I didn't touch anything and today it's slow again. I haven't run LiveUpdate so it couldn't be a BackupExec patch. Windows update has not installed any new patches, and I haven't installed any new drivers or programs on the machine. The only thing I've done between Friday and today is reboot the machine.
I'm backing up large files (8GB a piece) so it's not a lots of small files issue, nor is it a fragmentation issue as the drive is completely defragmented. Jumbo frames are enabled and the tape drive is currently the only iSCSI device attached to a single gigabit port (I have my SAN isolated from the rest of my LAN).
The connection is negotiated at gigabit, but it's only using 5% of the link instead of the 50% I was getting on Friday.
All in all, the backup is acting like the single block write mode is turned on again, but the box is unchecked in the device properties. I've even gone as far as uninstalling the tape device and reinstalling it with the latest 11d (7170) device driver package from the website.
