how to get the 72G capacity of my DAT72 tape for my backupexec ?

[Joseph_Chu_2]

Dear experts,
i found my backup tape can't use the maximum capactiy. i think it should be about to backup almost 70G data. i already enable the compression in that device. what do i miss ??
thanks!
Joseph

[Ken_Putnam]

DAT72 is rated at 72GB with data compressing at 2:1.

2:1 compression is a markeing dream, not an engineering promise. I generally figure on about 1.3:1 as a rule of thumb

If you are getting more thatn 36GB per tape, then compression is working

See also http://seer.support.veritas.com/docs/199542.htm

[Amruta_Bhide]

Hello Joseph,
Along with what Ken said, it also depends on what compression you are using and what you are backing up with compression enabled:

Hardware compression is done by the device itself. When you use hardware compression option on Backup Exec (BE), BE commands the hardware to go ahead with the compression. However the hardware compression depends on the device. The device should support Hardware Compression. We advice you to contact your Vendor for more information of the same.

Software compression is done by BE. It is said to achivachievepression of 2:1 but that ratio is hardly ever achieved. Compression can be highly variable depending on your input data, as the software compression depends on the type of file or data you are trying to back up. For example: Already compressed files cannot be compressed any further. And the compression for normal '.ttext files will be more than the compression of '.gif' or database files.

Hope that explains a bit. Let us know if you have any other Questions.


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Thanks.