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Slow performance on DLT8000 (8 MB/min)

Jonas Back_2
Super Advisor

Slow performance on DLT8000 (8 MB/min)

I'm having problems with the backup performance with a DLT8000 (DLT80e) on our system. It's a regular file backup (for testing, a single 250 MB file).

The systems I've tried it on is both Win2k, SP2 using built in backupprogram. Hardware:
1. HP LC3, PII-450 MHz, 2940AU, Promise Fasttrak IDE-RAID
2. HP Vectra P4-1.7 G, 2940U2W

This is what I've done so far:

- Updated firmware on DLT to latest
- Updated firmware on Adaptec to latest
- Re-installed SP on Win2k
- Tried another (new) HP DLT-tape.
- Made sure the termination is correct
- Not using the same SCSI-ID as other devices
- Tried backing up both from SCSI & IDE-drives
- Also tried HP Omniback with same performance problems
- Made sure performance of the server is not the problem. If I do a backup "to a file" instead, I get ~120 MB/min. Backing up the same files to DLT gives me ~8 MB/min.
- Sync transfer rate on the Adaptec is set to 80 MB/min (max)
- It's almost brand new

You can really hear the DLT spinning quite strange. Like it's spinning back and forth, just like the computer can't deliver data fast enough so it has to do that but I can't see that the performance of the server is the problem here.

Any ideas?
Vincent Farrugia
Honored Contributor

Re: Slow performance on DLT8000 (8 MB/min)


You might try to install this patch:

See Symptom No. 20 in this link.

You also have installation instructions in this link.

Replace "europe-support2" with "us" in the above link if you log in using the American site.

Tape Drives RULE!!!
Marco Hogeveen
Honored Contributor

Re: Slow performance on DLT8000 (8 MB/min)

Try running the Performance Assessment Tool.
It will diagnose the performance of your hardware to determine if that's causing the bad performance of your backup.
download it from:

Jonas Back_2
Super Advisor

Re: Slow performance on DLT8000 (8 MB/min)

I don't think the patch is the problem since I'm not backing up the System Disk. And I have the same problem with the built-in backupprogram in Win2000(which I rather want to use).

Here are the results from the Performance Assesment Tool is:

Transfer rate 10,34 MB/s
DLT80 Typical transfer rate: 6 MB/s

Transer rate 17,6 MB/s
DLT80 Typical transfer rate: 8 MB/s

That's quite high compared to my 8 MB/MINUTE :)
Marco Hogeveen
Honored Contributor

Re: Slow performance on DLT8000 (8 MB/min)

So it looks like the hardware is performing just fine.
Do you have the possibility to try a commercial backup application like backupexec or Arcserve?
A trial version of backupexec can de downloaded from
Which compression factor are you using?
What are the other setting in the adaptec SCSI controller? (like sync negotiation, wide negotiation, enable disconnect, etc).

Since you've updated the Firmware of the DLT, you must have used Library and Tape Tools.
Have you selected device analyes? It also might tell you what's going wrong.

harry d brown jr
Honored Contributor

Re: Slow performance on DLT8000 (8 MB/min)


If your scsi disk and scsi DLT are on the same chain, then you have to make sure that they are both of the same scsi class. For example if you have a scsi-2 disk and a scsi-3 DLT, then they are interfering with each other, forcing the scsi-3 DLT to have to retransmit each data packet in a scsi-2 format. I've seen systems be crushed by having different scsi class devices on the same chain. If you have access to another scsi card, then I'd suggest doing a test by moving the DLT to it and rerunning your benchmarks.

live free or die
Live Free or Die
Jonas Back_2
Super Advisor

Re: Slow performance on DLT8000 (8 MB/min)

Thanks for all your help guys!

Tomorrow we'll hook it up to our Omniback installation to see if the performance gets better.

I've done some more tests that might interest you in the meantime. I hooked it up to a HP LH3 server with a Adaptec 2940UW Pro. The disks on that server is hooked up to the builtin Symbios SCSI-card so the only thing on the Adaptec is the DLT. This system is running Windows NT 4.0 SP6. I installed the DLT and downloaded the drivers from the HP web. Same problem - 6 MB/s. The PAT says 136 MB/s on that system!

Also, system nr 1 also just have the DLT hooked to the DLT. The disks are on a IDE-RAID card. But it's a 2940AU (not wide), but the performance should be pretty good anyway right?

And it makes no difference on system nr 2 if I backup from the SCSI-drives (on the same channel as DLT) or the IDE-drives.

Here are the seetings of the 2940U2W-card
Sync Transfer Rate 80 MB/s
Initiate Wide Negotiation Yes
Disable Disconnection Yes
Send Start Unit Command Yes

I tried to find which settings are correct at HP website, but couldn't find it. You know?

On the 2940UW Pro card of the LH3r the Wide Negotation was set to No.

I used Library and Tape Tools but for now I only tried Read/Write test on system nr 2. The rate is still around 6-8 MB/min when you see it testing. I aborted the test because doing the all 2000 MB would take ages.

I will post more information tomorrow like the result of the other tests in Library and Tape Tools.
Jonas Back_2
Super Advisor

Re: Slow performance on DLT8000 (8 MB/min)

Sorry for not getting back for a few days.

I've insalled HP Omniback now and the performance is still very slow. I also triedd HP Tape and Library Tools and it reports no errors.

Maybe it's time to contact HP support or do you guys have any other ideas?