Re: 3.5" Disk archiving

[Andy McFadden <fadden@fadden.com>]

Jeff Blakeney <CUTjblakeney@sentex.net> wrote:
> Doing this isn't enough to get the smallest possible disk archive.
> You get the best compression if all the unused sectors are filled with
> zeros AND are grouped together sequentially on the disk.  If you use a
> "disk zap" utility to zero all the unused sectors you should also run
> a "disk optimizer" utility to get all the actual file data put
> together at the beginning of the disk and leave all the empty sectors
> together at the end of the disk.

You are correct, but I think you've reached the point of diminishing
returns.  ShrinkIt does an RLE pass before feeding the data into LZW,
so an empty 512-byte block is going to go down to nothing before LZW
even gets near it.  You're not going to lose a lot of ground by having
the RLE bytes in the LZW trie.

Of course, you could also argue that you will get better compression if
text file sectors aren't intermixed with binaries.  Copying the files to a
new disk should yield sequential allocation, which probably provides more
of a compression boost than clumping the zeroed blocks together.  For best
results you should copy different categories of files in different groups,
kind of like "solid" archiving in RAR.

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