On Sat, May 31, 2014 at 6:48 PM, Philip Worrall <philip.worr...@googlemail.com> wrote: > LZ4 is a lossless data compression algorithm that is focused on > compression and decompression speed. LZ4 gives a slightly worse > compression ratio compared with LZO (and much worse than Zlib) > but compression speeds are *generally* similar to LZO. > Decompression tends to be much faster under LZ4 compared > with LZO hence it makes more sense to use LZ4 compression > when your workload involves a higher proportion of reads. > > The following patch set adds LZ4 compression support to BTRFS > using the existing kernel implementation. It is based on the > changeset for LZO support in 2011. Once a filesystem has been > mounted with LZ4 compression enabled older versions of BTRFS > will be unable to read it. This implementation is however > backwards compatible with filesystems that currently use > LZO or Zlib compression. Existing data will remain unchanged > but any new files that you create will be compressed with LZ4. > > Usage: > Apply the following 8 patches to the current git tree > (as of 20140531) and compile/load the btrfs module. > > # mount -t btrfs -o compress=lz4 device mountpoint > > or > > # mount -t btrfs -o compress-force=lz4 device mountpoint >
I gave this patch-set a preliminary test, and there were no obvious signs of corruption. I was unable to run btrfsck or xfstests since btrfs-progs is not yet aware of lz4, so my testing should be considered superficial. One comment: IMHO, it would make sense to implement lz4 and lz4hc at the same time. Since both are now in the kernel, I assume we would go that direction eventually anyways, unless there are some wrinkles around lz4hc I don't fully appreciate. So we might as well conserve the kernel INCOMPAT flag. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
