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Backup issue

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by ksvijayb

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Hi,
I have a Compaq Proliant server with NT 4 runnings. HDD size is about 20 GB. Partitioned into 2 drives of 16Gb (D) and 4 GB (C).
I have the OS in C and Data in D drive.
I have a DDS3 tape drive to a backup data.
I have about 15.5 GB of Data now.
When I try to use DDS 3 12/24 data tape for backup, I am able to backup only about 13GB of data and then the system prompts for a new tape.
Why is this so?
HOw do I make use of the "Compression" fearture to save the data?
Any help is most appreciated.
TIA.

5 replies

by tech_wiz03

Compression is not an exacting science. where some files contain large ammounts of compressable space by replacing bytes in the files with a count byte and a byte to be repeated a certain number of times, other files do not. Your 12/24 tape is saying that uncompressed it saves at 12GB but under maximum compress you can have up to 24GB. In your situation you are able to save 13GB so some compression is taking place. Whether you are getting the best compression on a dds3 is something i can't answer.

by jschein

DDS3 drives are a hoot... I have one last standing drive that will get to 15gb and stop. After researching and calling and all that mess, come to find out most of my files were already compressed and some just could not be compressed. Hence the "half" full data tape.

Since that, I've replaced old servers with new and have gone to DDS4 / DLT / Ultriums ... The DDS4 is more flexible and reliable in it's backups than it's predecessing DDS3.

There is no fix as what it back ups and compresses, it does, what it does not... it wasn't meant to be.

Good luck.

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