On Mon, 13 Oct 2008, Richerland Medeiros wrote:

> How do I use the default compression hardware native of LTO4?
> I have 1.4 TB of data and the tape is full when it comes to 900GB.

You are using the default compression already, else it would be full at
~795Gb

Compression only works on compressable data. Whatever you are putting on
the tape has already been compressed.

2:1 compression claims are very optimistic and must be dismissed as
marketing puffery.

Most of us find that the real average is 1.2:1 on a full backup and higher
on incrementals (logfiles are _very_ compressable)

The only safe way to estimate how many tapes are needed for any given
backup is to use the native capacity of the tape. Compression is a bonus
which means you may use fewer, but don't count on it.

AB


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