Compression

[Louise_Cincotta]

I was trying to do a back up of about 42 GB and after about 32 GB is was wanting another tape. The tape and drive are supposed to be able to backup 36GB native and 72 GB compressed. I did not set this backup system up. I contracted a Value Added Reseller to install this system. In Backup Exec, in Devices, Stand Alone Drives, Properties, Configuration, Enable Compression is checked and Block size is set to 32k and Buffer size is set to 32k, buffer count is 10 and High water count is 7. These are the only settings that I can find that deal with compression. Why will it not compress the 42GB onto one tape? What settings do I need to set to make it compress?

[ray_littlefie1]

Couple of things to check:

Look at the media statistics for the tape you are using. If there are a lot of read/write errors, it may be that the tape is wasting space attempting to write to bad blocks, and is unable to hold it's rated capacity. Try a new tape.

Verify the backup job is set to use hardware compression or none .(Job Properties -> settings ->General).

Is the source data already compressed? (Check for "C" attributes in the folders/files) Sometimes attempting to compress data that is already compressed will cause files to bloat.

Almost all tape drive manufactuers state their drives are capable of 2:1 compression with an asterick or footnote at the bottom of the page; the real compression value is data dependent.

[Ajit_Kulkarni]

Hello,

To add to Mr Littlefield's reply please refer to the following technote:

Backups fail to get double the amount of the native capacity recorded to a media, even when hardware compression is being utilized.
http://support.veritas.com/docs/199542

Regards


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