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Re: My Monthly archive config - issue (Trying to source and use a tape changer if possible)
2005-09-30 11:53:23
Chuck Amadi Systems Administrator wrote:
I am using DDS-4 DAT tapes 20GM native and 40GB compression So I hope
amanda using
and amanda, using gzip, can probably put well over 40GB on the tape if
your are correct.
No, that won't work out. First of all, 40GB compressed is a purely
imaginative figure that marketing pinheads have come up with in order to
impress clients. It has no basis in reality; in fact they assume that
your data is compressible (which might or might not be the case, but
read on), and that it compresses at a 2:1 ratio (which will not be the
case in real life).
If you plan to use software compression via gzip, the data you feed to
the tape is not compressible at all; the DDS' hardware compressor will
actually expand the data before writing to tape, giving you an effective
capacity of much *less* than 20GB after gzip compression, or just a
little more than 20GB before gzip.
Just use one *or* the other of hardware and software compression;
general consensus on the list is that software compression is better if
you can spare the cycles. Look in the archives for reasons if you are
interested.
Alex
--
Alexander Jolk * BUF Compagnie * alexj AT buf DOT com
Tel +33-1 42 68 18 28 * Fax +33-1 42 68 18 29
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