Problem with Storage Works tape drive

[Ivakin Dmitry]

Hello All!

I have Windows 2000 SP3, NTBackup, HP Storage Works dlt vs80, tape DLTtape IV Data cartridge. I know that I can copy 40GB information in normal state and 80GB in compression state. My current backup set is 52Gb.
So, I created backup set, turn on hardware compression (sure!), but after somewhile I have message "The tape is full, please put the new tape". Why it's happened??? Could you advice me? Thanks in advance!

[Marino Meloni_1]

Hello Dmitry,
yes the native capacity in normal condition is 40 Gb on one tape,
but the 80 Mb in compressed mode is oly related to the ability to compress your data with a ratio of 2:1, that means that if your data are uncompresable or less compressable, the max amount of data that you will be able to store on one tape will be reduced.

[Ivakin Dmitry]

What do you mean? Is it impossible to put 52GB to tape? It's backed up about 50GB to tape, and after requests for new tape. What I should do to make normal backup in this case? Thanks!

[Marino Meloni_1]

40 Gb is the native capacity of a VS80 DLTiV tape.
the recording system on a DLT tape is Digital, that means that the space on the tape is fixed, like on a HDD, you have cluster recorded on the tape that are a certain amount. It is not like Videorecorder, where you can ad more info jus slowing the speed of the tape.

So if the number ofcluster is fixed, the only way to increase the capacity is to compress data (removing recurence and free space). Due to the portability of tapes, the compression algorithm is fixed since years, (unlike softwares like Winzip Winrar that evolves during the time).

If you cannot store more than 50 Gb on a tape that means that you cannot compress your data more than ~1:1.2 .
This in a normal environment.

Other factors that can waste space on a tape are bad blocks (bad quality tape) or Drive in nons treaming mode.

Marino

[Ivakin Dmitry]

OK! Today I will exclude some folders with big zip files, etc. May be it help me.

Thank you very much for your help!!!