Re: 3.5" Disk archiving

[Jeff Blakeney <CUTjblakeney@sentex.net>]

On Sat, 15 Feb 2003 10:03:24 -0500, "Tom Zuchowski"
<tzuchow@attglobal.net> wrote:

>Quite often, disk archives are larger than the UNCOMPRESSED file contents of
>the original disk!

I don't think I've ever seen it get that bad but it is possible if
there are few files and and/or lots of unused sectors that aren't
filled with zeros.

>Having done about a zillion disk archives for Genie when I was a librarian
>there, I have to say that it will be a very rare occasion when a disk
>archive is as small as a file archive.

True, the chances of a disk archive being smaller than a file archive
is quite small but it is still possible.

>Here is why: ShrinkIt archives the
>ENTIRE disk, including all of the "empty" sectors. Erasing a file does not
>remove it from the disk, but merely deletes it from the disk catalog. If the
>disk has seen activity where files have been erased, many of those "empty"
>sectors will have old data in them. This erased data becomes a part of the
>archive, increasing its size. For DOS 3.3 disks, the problem is even worse
>as DOS itself becomes part of the archive.
>
>The only way to avoid this is to format a fresh floppy, copy all of the
>files onto it, and archive it before any files are erased. For DOS 3.3,
>further savings can be realized by using Copy II+ or equivalent utility to
>make a DOS-less disk.

That's the method I suggested in one of my previous posts.  I did
forget about the fact that DOS 3.3 adds an extra 48 sectors (tracks 0
to 2) as well as the catalog sectors so DOS 3.3 disks will almost
never be smaller than a file archive.

However, ProDOS only adds an extra 7 or 8 blocks to the actual file
data (unless there are subdirectories on the disk which will add at
least one more block per subdirectory) so there is a better chance
that these disk archives could be smaller than a file archive.  The
chances increase if don't include the PRODOS and/or BASIC.SYSTEM files
which you aren't supposed to redistribute without a licence anyways.
:-)

-- 
 Jeff Blakeney - Dean of the Apple II University in the
                 Apple II Community on Syndicomm.com
 CUT the obvious from my address if you want to e-mail me