compression of tar file

[apple]

Dear All,
what is the compression of tar file, if I have a directory of 90GB, how much space I need to provision for this directory to be tarred?
Hope to hear from you. Many thanks

[Steven Schweda]

> what is the compression of tar file, [...]

Everything depends on the data. If you can
run a test on a representative sample of the
data, then you may learn something useful.
With no knowledge of the data, only guesswork
is possible.

Here are two files:

dyi # ls -l file?.dat
-rw-r--r-- 1 root sys 4096 May 24 22:05 file1.dat
-rw-r--r-- 1 root sys 4096 May 24 22:09 file2.dat

Here are the same files after gzip compression:

dyi # ls -l file?.dat.gz
-rw-r--r-- 1 root sys 4129 May 24 22:09 file1.dat.gz
-rw-r--r-- 1 root sys 106 May 24 22:09 file2.dat.gz

One was reduced by about 40:1, and the other
one grew a little. My psychic powers are too
weak to tell me how well your data can be
compressed.