07:06, Maciej Marcin Piechotka wrote: > On Mon, 2011-09-19 at 10:53 +0800, Li Zefan wrote: >> Maciej Marcin Piechotka wrote: >>> I've noticed that: >>> >>> - with x86-64 Fedora 15 DVD install images: >>> - du -sh <ROOT VOLUME> was 36 GB >>> - btrfs df | grep -i data have shown over 40 GB used >>> - without >>> - du -sh <ROOT VOLUME> is 34 GB >>> - btrfs df | grep -i data have shown less then 34 GB used >>> >>> It seems that iso files are considered compressable while they may not be (and penalty is severe - 3x). >>> >> >> With compress option specified, btrfs will try to compress the file, at most >> 128K at one time, and if the compressed result is not smaller, the file will >> be marked as uncompressable. >> >> I just tried with Fedora-14-i386-DVD.iso, and the first 896K is compressed, >> with a compress ratio about 71.7%, and the remaining data is not compressed. >> >> -- >> Li Zefan > > Just a question from person who don't know how btrfs operates - what if > the beginning of file is well compressable and the rest is not? > It's explained in the previous mail - the beginning part will be compressed, and the rest will not. > In any case the compression was my uneducated guess where is missing > 4GB. > It probably has nothing to do with compression. You can try without compress=lzo, and see if the issue still exists. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
