Hello,
On 5/19/2006 9:59 PM, Georger Araujo wrote:
Sure, but a tape has a fixed number of blocks;
Unfortunately, not.
I think
it would be possible to know how many of them are used
and how many are left?
The compression rate isn't the most important factor -
say you have a 200 GB tape divided in 200 blocks, each
1 GB in size (insane, yeah). If Bacula wrote up to the
100th block in the last backup, it doesn't really
matter if I have 100 GB of uncompressed data or 500 GB
of compressed data; what REALLY matters is that I can
write AT LEAST more 100 GB to the tape, because I have
100 blocks left.
That's not how hardware compression for tapes work. You write blocks of,
say, 1 GB to to tape, and depending on how good that data can be
compressed the length of tape (usually, the length of the track(s)) used
vary. You really can't know how much data fits on a tape before
measuring it, and if hardware compression is on your results areonly
valid for your test data.
Softwarwe that claims to know exactly how much tape space is left
usually lies, or, expressed differently, estimates. By the way: I wrote
a small perl program to estimate available tape space, based on how much
data is stored on tape volumes with comparable characteristics (i.e.
Media Type).
Arno
Regards,
Georger
--- Ryan Novosielski <[EMAIL PROTECTED]> escreveu:
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Hash: SHA1
You can't really tell how much free space there is,
because you can't
really tell how well the data you're going to write
will compress.
Ryan Novosielski -
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