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DLT problems

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8 replies

by donald.pijpstra

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Picture this:
- An IBM Netfinity 5600 with about 50Gb to backup.
- A Quantum DLT 8000 backup device
- Seagates Backup Exec 8.0 software
The Problem: The throughputrates differ from 400Mb to 20Mb per minute. One time the backup will take maybe 6 hours and the next time after 20 hours it still has not finished.
First I had the DLT connected to a seperate IBM NF 3000 with Ultra160 SCSI controller functioning as backupserver. There I had the same problems. At some point the DLT has been replaced with another DLT of the same model but the problems continued. So I moved the DLT and connected it directly to the NF 5600 containing the data. So now I have a different server, a different DLT device, a different SCSI controller with different cables and and a fresh BUexec installation and the problems remain. I tried both the drivers coming with the Seagate software and the drivers which I found at Quantum. I also tried different blocksizes for the DLT with BackupExec but I see no improvement with any of the settings. So before throwing the DLT out of the window Who Has The Golden Idea ????

8 replies

by cavedweller

Is the SCSI bus terminated properly? Is the DLT directly connected to the interface with an 'ultra' cable (no other devices in the chain)? If you use the SCSI card's diagnostics does the DLT show up with correct make/model, etc. How about the detected transfer rate? Perhaps setting it manually, if possible. You might also try the various BE compression settings (hw/sw).

Veritas (Seagate) has a tech note but it seems to cover older drives and BENT 7.x. Here's the url anyway: http://support.veritas.com/menu_ddProduct_BEWNT.htm
What can be done to increase performance with Backup Exec for Windows NT and a Quantum DLT tape drive?
TechNote ID: 190783

Good Luck!

by spydergst1

You have answered most of the questions which need to be asked. It's not hardware you addressed that. Its not the LAN you addressed that. The answer lies with the backup itself. Allow the backup software to compress the data. This will make it run just a little faster. I think the backup has problems because of open files and/or active client session on the server. Test to verify. Make sure no one is logged in and no files are open try the backup and see what happens then, the next time the backup runs long see if there are open files or logons.

Perhaps someone runs a some process which along with the backup kills the servers perfomance.

There is no easy way around it (unless someone has the answer off the top of their head) you will have to do some testing and monitor server performance.

good luck

by donald.pijpstra

Yesterday the DLT has been replaced again and it was decided that the problem was caused by a defect SCSI adapter causing after a while problems on the DLT. Now the backup is running normal again. Thanks for you reply.

by maxtec

As what have been done should be isolate away all the hardware and connection problems. That should say the problem is on the Software and environment.

The normal NT Backup or Basic Veritas Backup Exec only backup the flat files.
During the backup running, if happen the still have the Network user logon session or the files are open for use.
Then the backup process time will take longer than normal. It will wait till the session end or files been close.
.
To resolve this, you may can consider purchase the Open File Option from Veritas.
This is let you be able to backup the files or session still active.
.
May also can work as, backup during no body access the files and the Server.
.
Hope this is useful.
.
Regards

ThomasNG
Open File Option

by donald.pijpstra

Also this advise unfortunately did not work out. I switched on the Open File option and saw a slight improvement (from 20 to 28Mb per minute) but this rate (20*60=1.2Gb per hour) is nothing compared to the 20Gb per hour I reach occasionally using the same setup. Remember sometimes the performance is quite reasonable.

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