Al said:
[QUOTE="John said:
Some picture formats, like jpegs for instance, are already
compressed, thus you can't compress them anymore. Try a graphics
format that isn't already compressed like bitmaps, etc..
Phil. I have been trying to find more about this in a different post
regarding the practice of using drive compression from properties of
the drive. Rather than compressing individual file formats I am
concerned about the effect photos that exist on such a drive. Will
other files be compressed and jpegs will not or will all files be
compressed equally. Thanks for any comments.
J.
NTFS compression is great. I've been using it in serious business
environments to almost 10 years.
There's two types of compression; "Lossless" and "lossy" and all
compression software (algorithims, really) fall into one or the other
type.
ZIP is an example of lossless compressition. Yoiu always get back
exactly what you put in, and you can compress/expand as many times as
you want.
JPG is a lossy compression, you lose a little each time you compress.
NTFS compression is like ZIP. it doesn't change your data.
(Avoid the compression feature in Windows 98, not that it's lossy.
its buggy, from what I,m told.)
In the bad old days of 400MB C drives, we used NT, and I routinly
compressed the entire C:\ drive. The only file it couldn't compress
was \pagefile.sys. As a hack, I once ran an Oracle database on a
compressed file system. It worked, but there are lots of reasons not
to do this at home. These daya I make TMP compressed, out of habit.
The only type of data that shoudn't be compressed is data files that
are updataed in-place, since each time a record is inserted the
recompressiom may not fit in the same cluster, think of it as the
worst file fragmentation you could imagine.
The tests I've done show there is no performance hit for compression.
The CPU time to compress is offset by the faster I/O because the file
is smaller. In one extreme case (Gigabyte-size numeric files that
compressed 20:1) The server application ran much faster.[/QUOTE]
Thanks for this great education on much of what I really needed to know. I
probably should at some point sit back and read up on just this topic. I
still am wondering about exactly what goes on when I find my drive
compressing itself without any configuration by me. I first noticed that
files were indeed compressed with I was in the process of 'cleaning' said
HDD. I saw files in the temp folder and recycle bin and files in the
compression section. I canceled the compression process while it was in
progress and was taking what might have been several hours to complete. I
then wondered where these files were going and would I have to uncompress
them to view or use them. I do not have the box checked that allows the
drive to be compressed but yet I still see the 'compressing drive to save
space' dialog when I click 'clean drive'
J.
