Re: Compressed Folder

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From: Al Dykes (adykes_at_panix.com)
Date: 01/09/05 

Date: 9 Jan 2005 11:45:54 -0500

In article <u450Icm9EHA.1400@TK2MSFTNGP11.phx.gbl>, John <Unlisted> wrote:
>Phil wrote:
>> 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 performace 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 HUCH faster. 

-- 
a d y k e s @ p a n i x . c o m 
Don't blame me. I voted for Gore.

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