On Fri, May 17, 2002 at 10:28:06PM +0100, Niall O Broin wrote:
>
> You must bear in mind that a DDS-3 tape holds 12GB and NOT 24 GB of data,
> despite what the marketing scum might like you to think. They "assume" a
> compression ratio of 2:1 which I've never heard of ANYONE achieving (apart
> from tape drive manufacturers in their contrived tests).
I don't know, varies greatly with the data. Here are the results of the
last full dumps of my disklist entries:
butch /w/jg1 0.20
butch /opt 0.35
butch /w/tape8 0.35
winnie / 0.37
butch / 0.40
butch /usr 0.41
butch /w/dutch 0.45
butch /w 0.53
butch /win/c 0.55
butch /export 0.62
butch /u 0.69
butch /var 0.70
winnie /cygdrive/c 0.72
butch /images 0.73
butch /u2 0.79
winnie /cygdrive/e 0.91
winnie /cygdrive/d 0.93
winnie /cygdrive/f 0.96
butch /w/InstPkg 0.97
butch /w/Packages 0.97
butch /d2 3.20
butch /d4 3.20
Anything under 0.5 is a 2:1 compression ration.
One gave nearly 5:1. And of course several
file systems were virtually uncompressible.
It demonstrates the difficulty of guessing
the hardware compressed capacity of a tape.
BTW the last two entries are anomalies of
totally empty file systems.
--
Jon H. LaBadie [EMAIL PROTECTED]
JG Computing
4455 Province Line Road (609) 252-0159
Princeton, NJ 08540-4322 (609) 683-7220 (fax)
