DLT VS80 - media failed to mount

[Brad Dickey]

NTBackup on our MS Windows 2003 Small Business Server has failed for the past few days with the error "requested media failed to mount".

Backups were working fine until total bytes backed up exceeded ~42,000,000,000. When we cleanup disk space so that total bytes are less than 42,000,000,000 backups complete without error. It appears that the DLT VS80 hardware compression is perhaps not working?

This tape drive should be able to store ~80Gb on one tape. We do not compress our disk; LTT reports no problems with the DLT VS80; h/w compression shows to be enabled; the SBS backup script is configured to use h/w compression if available.

Any ideas or help for troubleshooting and problem resolution are greatly appreciated!

Brad Dickey

[Torsten.]

The capacity depends on if your data is compressible or not.

The drive has a maximum native storage capacity of 40 GB, up to 80 GB, assuming 2:1 data compression.

http://h18006.www1.hp.com/products/quickspecs/11403_div/11403_div.html

If you try to write already compressed data to the tape, you probably won't exceed ~40GB.

[Brad Dickey]

About half the files are .exe's or .dll's, the other half are various user data files - Word & Excel documents. None of the files are compressed, and disk is not compressed.

I suspect that the DLT VS80 hardware compression is not working, but do not know how to verify this?

[Jacob Zeeman]

Hi Brad,

You can run a Compresstion Test in LTT. Once it completes on the Test Results tab it will report to you the compression ratio.

This is the best way to determine if the hardware compresion algorithm is functioning properly.

Here is the user guide for LTT, in case you need further assistance with running the tests.

http://h20000.www2.hp.com/bizsupport/TechSupport/CoreRedirect.jsp?redirectReason=DocIndexPDF&prodSeriesId=406729&targetPage=http%3A%2F%2Fh20000.www2.hp.com%2Fbc%2Fdocs%2Fsupport%2FSupportManual%2Fc00172321%2Fc00172321.pdf

Hope this helps.

Thanks,
Jake Zeeman
HP Server Storage Specialist

[Torsten.]

Make sure to enable "use hardware compression, if available" within your backup software.

[Brad Dickey]

Jake & Torsten,

Thank you for your suggestions.

I ran the LTT Compression Test this morning and the drive "passed", reporting a compression ratio of 2.27:1 on the 600Mb test file.

Backup still fails when more than 42,000,000,000 bytes are written to tape. I tested compressability of the data going onto the tape by "zipping" about 1.7 Gb of user data and acheived appx 2:1 compression.

It looks like the drive is working correctly, and the data appears to be compressable, but the backup regularly fails at the same point. Any additional ideas?

The server is an HP ML360 wit 72 Gb disk storage and 512 Mb RAM.

Thank you,
Brad