Re: [PATCH] LogFS take three

Arnd Bergmann
2007-05-17T21:37:23Z

On Thursday 17 May 2007, Pekka Enberg wrote:
>
> Jörn Engel wrote:
> > Compressing random data will actually enlarge it.  If that happens I
> > simply store the verbatim uncompressed data instead and mark it as such.
> >
> > There is also demand for a user-controlled bit in the inode to disable
> > compression completely.  All those .jpg, .mpg, .mp3, etc. just waste
> > time by trying and failing to compress them.
>
> So any sane way to enable compression is on per-inode basis which makes
> me still wonder why you need per-object compression.

1. it doesn't require user interaction, the file system will do the right
thing most of the time.

2. enlarging data is a very bad thing because it makes the behaviour
of the fs unpredictable. With uncompressed objects, you have a guaranteed
upper bound on the size.