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Heatshrink compressed drives? - Tamp ISO compression test (Announce)

posted by mceric, Germany, 01.02.2025, 13:54
(edited by mceric on 01.02.2025, 14:07)

> This might be more of a possible target for deduplication than
> compression.
>
> As Linux has file systems that support deduplication: how about testing
> this on BTRFS or ZFS?

I have tried to find out whether RLE would be useful for the ISOs, assuming that the encoding is "prefix + N bytes to copy" or "postfix to repeat last byte/word/dword N times". The -1st byte/word/dword of each sector is assumed to be 0.

What bothers me is that I find only 1/9 of the expected all-sector-zero or -same in the thesis ISO, for example.

For the 2007-09-06 fdbasecd, the difference is smaller: I find 4.2% of the sectors to be all-zero (and none all-same-some-other-value, by the way) but TAMP compresses 4.7% of the sectors to zero compressed size.

Still, the difference might be 0.5% "sector is same as previous sector" which should not compress to zero size in a system where you expect each sector to be decompressible without needing other sectors as context.

So you might be right that the compressor state did not get reset between sectors, as there are unrealistically many sectors compressing to a size of zero?

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FreeDOS / DOSEMU2 / ...

 

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