Re: Hardware vs. Software Compression
1999-10-01 17:13:16
Here is an example of what can happen when you compress files that are already
compressed. This example is using software compressions on a Unix system using
2 different utilities: compress and gzip.
Origional file.
-rw-rw-rw- 1 root sys 50339840 Oct 1 15:36 usr.tar
Unix compress utility.
Unix compress utility.
Compressed, compressed again, and compressed 3rd time.
-rw-rw-rw- 1 root sys 26751013 Oct 1 15:38 usr.tar.Z
-rw-rw-rw- 1 root sys 33438204 Oct 1 15:41 usr.tar.Z.Z
-rw-rw-rw- 1 root sys 33438204 Oct 1 15:41 usr.tar.Z.Z
-rw-rw-rw- 1 root sys 39067782 Oct 1 16:00 usr.tar.Z.Z.Z
-rw-rw-rw- 1 root sys 39067782 Oct 1 16:00 usr.tar.Z.Z.Z
gzip utility.
gzip utility.
Compressed, compressed again, and compressed 3rd time.
-rw-rw-rw- 1 root sys 18601090 Oct 1 15:44 usr.tar.gz
-rw-rw-rw- 1 root sys 18287838 Oct 1 15:46 usr.tar.gz.gz
-rw-rw-rw- 1 root sys 18287838 Oct 1 15:46 usr.tar.gz.gz
-rw-rw-rw- 1 root sys 18290584 Oct 1 15:53 usr.tar.gz.gz.gz
-rw-rw-rw- 1 root sys 18290584 Oct 1 15:53 usr.tar.gz.gz.gz
Compressed file from compress compressed again by gzip utility.
Compressed file from compress compressed again by gzip utility.
-rw-rw-rw- 1 root sys 25173084 Oct 1 15:49 usr.tar.Z.gz
What happens depends on the algorithm used. It would be
What happens depends on the algorithm used. It would be
interesting to here from Sony (AIT), IBM (Magstar) and Qauntum (DLT) how
their compression systems handle data that's already compressed.
rick
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Richard L. Rhodes e: rhodesr AT firstenergycorp DOT com
Richard L. Rhodes e: rhodesr AT firstenergycorp DOT com
Ohio Edison Co. p: 330-384-4904
f: 330-384-2514
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