Compaq DLT7000 Compression problem

[Andrew Szasz]

I have installed a used Compaq-branded DLT7000 (35/70GB DLT), with an Compaq-branded Adaptec AHA-2940U2 in a (non-Compaq) machine running Win 2003 server. Drivers were automatically installed and backups work with NTbackup.exe Problem is that it appears that little or no compression is achieved (I receive no feedback on actual compression ratios from ntbackup). 3rd party compression tool shows that compression is possible with the files in question. Using Density Override button on front bezel shows compression is on, but has no effect. I am wondering if the W2K3 drivers do not support compression in NTBackup? thanks to anyone who can shed light~

[Marino Meloni_1]

even more often, the OS and the application try to optimise the files, and high compression ratio to the tape is even more difficult to reach.

I can suggest you to run L&TT to troubleshoot, there is a compression test that will let you know if the chip in the DLT is working or not, and you can also use some test to create 60 GB data with compression 2:1 then backup them to a 35/70 GB cartidge, and see if you can store it on the tape. This is the final test I use when there is compression trouble.

Take also in mind that space on the tape may be lost due to bad blocks, (old/damaged tapes) or drive not streaming (fragmented files, or backup via lan)

marino

[Andrew Szasz]

Thanks for the suggestions. I ran the L&TT tests and the health test reported everything working ok. It is a great utility, thanks for telling me about it.
I have tried more than one tape so I suspect it isn't a bad block issue.

[Andrew Szasz]

Attached are the three reports. the density select test gave dubious results.

[Marino Meloni_1]

I never used Xtalk utility from Quantum, but the result seems good, no major errors, just some recovered errors in the log

marino

[Marino Meloni_1]

I remember that there is a know problem with w2003 and RMS, this service interfere with backup operation and with compression.
There is no fix at the moment from Microsoft which is aware of the problem.

What it happens is that even if you stop and disable the service, it will have some component that will be active.

A workaround suggested by HP waiting for Microsoft Fix is to start and stop this service every time you reboot the server. doing this you are sure that this service is stopped and cannot interfere

marino