Two issues with compressed backup

[Henriquecicuto]

I have two problems with my backups devices running into ArcServe 11.5.


Issue1 )I have a HP StorageWorks SSL1016 Tape library with LTO-2 Ultrium tape drive. The tapes being used are Ultrium 2 200/400.
ArcServe shows that hardware compression is enabled, and I can´t turn it off (according to official docs, that is the behavior for tape libraries). Not a problem there. I already tested data compression using HP StorageWorks Tape and Library tools, and it showed a 2.26:1 ratio.
The thing is when I start my backups. The total amount is 860GB, and it´s taking 6 tapes. When I check the tape utilization reports, it shows me that none of the tapes is recording till 200GB. I get a maximum of 170GB and a minimum of 140GB. Since data compression is enabled, it should at least record till the standard 200GB, shouldn´t it? Or am I mistaken?

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Issue 2) Another server has an external DLT drive, using single DLT IV 40/80 tapes. With this drive the problem is the opposite. I can´t turn compression off. I already tried Erasing, Erasing Plus and then changing compression mode. When I format the tape, compression gets activated again. This is taking the backup over 10h to complete (and it´s only 38GB). I also tried a Full Erase, but it took a full night to do it (over 10h), and when it completed the tape still had its label on it. What should I do?

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I don´t know if those issues are complex or just if I´m missing something obvious, but I´m far from being a backup/ArcServe expert. I wanted to check ArcServe´s compression ratio, but I couldn´t find anything about it anywhere.

Thank you very much for your attention

 

[davidmichel]

check the database media view for soft write errors.
Check with HP for firmware updates.
All else fails ck with HP support.

Compression is controlled via the software (ARCserve).
To force ARCserve to maintain non-compression for a tape.
It should work by:
Quick Erase +
Turn Compression off
Formate the tape

If that does not work then take the extra set of deleting the tape from the database after erasing.

Compression ratio is determined mostly by the type of data processed. There is no set ratio for hardware or software compression. The ratio provided by drive manufacturers is set by the marketing heads and just the figure they like to use, but in no way should be considered reality.