Compressed partition or block device?

Christopher Browne cbbrowne-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org
Mon Jul 9 21:15:47 UTC 2012


On Mon, Jul 9, 2012 at 4:24 PM, William Park <opengeometry-FFYn/CNdgSA at public.gmane.org> wrote:
>> After all you don't want to just compress the disk from one end to the
>> other, since then any change in the middle would require recompressing
>> everything after it.  So that means it needs more of a per block level
>> of compression, but now the question is how to place compressed blocks
>> on the disk in an efficient manner given they will vary in size.
>> ...
>
> Hmm, good point.

There's another issue...

If the entire disk was a single compressed stream, then *any* disk
failure would lead to utter destruction of the whole filesystem.
Generally speaking, later bits are dependent on earlier bits, and so
losing a few bits near the beginning means you can't decompress the
later material.  That's a pretty horrible risk to take!

If you compress on a per-file basis, that risk gets spread out so that
it's more of a "dull roar" rather than "betting the filesystem."
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