[SDBUG] How to fill my tape to see how many data can i write to him?

[Michael J McCafferty]

Pedro,

According to 
http://h18006.www1.hp.com/products/storageworks/ultrium232/index.html 
that drive has a compressed capacity of 200G. That is a back of the 
envelope calculation that the marketing department strong-armed an 
engineer to give them once upon a time. It's double the uncompressed 
number, which is the "real" number of 100G uncompressed. The 200G 
number is estimated for marketing purposes. Every backup tape/drive 
maker uses the same 2x uncompressed number.

It depends on what kind of data you are backing (how compressible it 
is), but 180G is probably a good number for a real world backup to a 
tape that is marketed with a capacity of 200G compressed. Large text 
files compress very well but data that is already compressed will not 
(ie: JPG, GIF, WMV, anything .gz, .tgz, .zip or .Z), compiled 
binaries usually don't compress well either.

How do you write data to a tape to see if it fits 200G ? Well, if you 
write any other data other than the data you already wrote to it, the 
number will be different. The tape itself actually only fits 100G, 
but it was compressed to get the 180G on there.

Mike


At 02:16 PM 5/28/2007, you wrote:

>  Hi people.
>
>     I have 1 tape HP storage-works 232, i want to know how can i 
> write data to the tape and see how much data can freebsd write to 
> my tape? Not using bacula commands just Unix commands.
>
>     It supposes that supports 200GB, but i have problems with 
> bacula and i want to know if is bacula or freebsd. Bacula says that 
> "Tape Full" but calculating each client space, i only need 180GB, 
> then why is telling me that the tape is full.
>
>     How you could point me how to test my device, thanks all for your time!!!
>
>P.S. FreeBSD 6.1-p16 Bacula 1.38.11 MySQL 4.1.
>_______________________________________________
>SDBUG mailing list
>SDBUG at sdbug.org
>http://lists.sdbug.org/mailman/listinfo/sdbug

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