On most machines (most here means machines with 8 Mb RAM or more and a clock speed of 20 MHz or more), the speed of the floppy drive will be the limiting factor for the speed of tbackup.
Tbackup usually has the next part of a compressed archive ready before the writing of the current part is finished, except maybe when working on a directory containing a lot of small files.
On slower machines however, the time it takes to make a part may be (much) longer than than the time needed to write it.
If you find that part creation is too slow on your machine, you can speed up the compression process by reconfiguring tbackup. Of course, if tbackup spends less CPU time compressing it will produce larger archives, so there is a tradeoff to be made here.
First, here are some general comments about performance:
.z .gz .Z
.taz .tgz .tzg
.gif .arc .zip .zoo .lha .jpeg .jpg
A list of these extensions is kept in the /etc/tbackup/Compr.ext
configuration file. If you have many compressed files with an
extension not listed above, (e.g. .mpeg
), it may pay off to add this
extension to the /etc/tbackup/Compr.ext
file.
X386
,
emacs
, ...), so that
there is a lot of free RAM to do disk caching. A small amount of
extra disk cache can sometimes increase performance by a large
factor./etc/tbackup/Config
. This file should be pretty much
self-explanatory, the relevant part is included below:
#The lines below determine the computation time/compression ratio
#tradeoff factor, as used in the `afio' pack method.
#
#Select the appropriate two lines or alternatively experiment until you
#have found a setting you like.
#The two parameters are the values for the afio -G and -T options,
#see the afio manual page for more information.
#Uncomment these settings for machines like a 486/33 with 8 Mb or better:
export gzipspeed=6
export threshold=512
#Uncomment these settings for machines like a 486/16 or 386/33 with 8 Mb:
#export gzipspeed=5
#export threshold=3k
#Uncomment these settings for machines like a 486/16 or 386/33 with 4 Mb:
#export gzipspeed=2
#export threshold=5k
#Uncomment these settings for slow machines without much memory.
#export gzipspeed=1
#export threshold=8k
Note that I have no magical way of guessing the i/o speed / CPU speed
ratio on your machine. It may well be the case that you need to
uncomment the last entry to get a good backup time/compression ratio
tradeoff on your 386/33 8Mb machine.
Experiments on my machine show the following tradeoff figures:
gzipspeed threshold cpu time used archive size
6 512 100% 100%
5 3k 60% 106%
2 5k 40% 113%
1 8k 25% 125%
no compress, afio0: 14% 178%
These figures are probably completely meaningless in the general case:
they do not only depend on the i/o speed / CPU speed ratio but also on
the kind of files in the archive.Next Chapter, Previous Chapter
Table of contents of this chapter, General table of contents
Top of the document, Beginning of this Chapter