Ok I have a very annoying speed issue that I have been trying to resolve for the past few days. Basically I am getting 1.86 mb/sec backup speeds, regardless of compression ratio. I have tested with 2:1 and 3:1 and the speed doesn't differ one tiny bit, it's still 1.86 mb/sec.
Before people say, I have read and followed all of the following document: http://seer.support.veritas.com/docs/231488.htm
I have ran HP diagnostic tools and can read from one hard drive (source) on average 9mb/sec and the other, 29mb/sec. Yet backing up to the tape is 1.86 mb/sec.
Note that the HP diagnostic software writes data into system memory and then backs this up to the tape, to elimate SCSI disk issues, and still... 1.86 mb/sec. The drive is a HP Ultrium drive that has a specification of 900mb/min, so this is far under achieveing in its current state.
CPU/Memory isn't even getting close to its limits, CPU was around 11% and memory had over 280mb free.
Controller is set to Wide Negotiation with auto detect speed. It's an Adaptec 29160LP Ultra 160 SCSI card that has no other devices other than the Ultrium drive on it. The cable is all of a few inches long and is of the 68pin variety. I have just tried updating the drivers for the Adaptec card but cannot reboot yet as it's a live/production server.
The thing that amazes me is the consistency of it, regardless of source. Something somewhere is definately throttling the bandwidth on the card/channel/tape drive to 1.86mb/sec...but what? and how can I find out? As stated, I have followed many documents to try and troubleshoot this.
This issue really is driving me mad, can somebody please give me a straw to grasp hold of? To be honest though, I'll be suprised if I get a reply as I've tried as good as everything documented on this site.
Thanks