Dan Mick writes: > Robert Milkowski wrote: > > Hello Dan, > > > > Tuesday, April 17, 2007, 9:44:45 PM, you wrote: > > > >>>> How can this work? With compressed data, its hard to predict its > >>>> final size before compression. > >>> Because you are NOT compressing the file only compressing the blocks as > >>> they get written to disk. > > > > DM> I guess this implies that the compression only can save integral > > numbers of > > DM> blocks. > > > > Can you clarify please? > > I don't understand above.... > > If compression is done block-wise, then if I compress a 512-byte block to 2 > bytes, I still need a 512-byte block to store it. > > Similarly, if I compress 1000 blocks to 999.001 blocks, I still need 1000 > blocks to store them. > > This is not a significant problem, I'm sure, but it's worth remembering. > Many tiny files probably don't benefit from compression at all, rather than > "only a little". >
I guess this is true for sub sectors (512 Bytes) filesize. But for anything else, we could seen gains. -r > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
