LZ4 For Btrfs Arrives While Its FSCK Remains M.I.A.

The proper fsck utility for the Btrfs file-system remains M.I.A. while a contribution from an independent developer introduces LZ4 compression support to this next-generation Linux file-system.

Last month at SCALE 10x the lead developer of Btrfs, Chris Mason, told the crowd that an error-fixing Btrfs.fsck tool was imminent since the file-system is going production-ready in Oracle Linux (Mason is an Oracle engineer) and had a deadline of 14 February.

As Phoronix readers noted this weekend when I wrote about a patch that can make Btrfs write 5~10% faster, the proper Btrfs fsck tool is still missing.

Some have speculated that the new Btrfs tool is currently undergoing behind-closed-doors review at Oracle. "btrfsck is going through QA internally at Oracle. It needs to be _safe_ before being released. Another thing is that Feb 14 was likely a deadline for Oracle (for proper QA) more so than a deadline for public release."

Meanwhile published this past week was support for LZ4 transparent compression in Btrfs. The LZ4 compression support comes after the original transparent Gzip file-system compression, LZO compression, and most recently was Google Snappy compression support for Btrfs that will land in the Linux 3.4 kernel.

The benchmarks published by the LZ4 patch submitter, David Sterba, in his mailing list message indicate rather nice results for LZ4 with Btrfs compared to the Snappy compression method, which is similar to LZO. Though results from some Btrfs contributors have questioned his benchmarks and calling them unbelievable, etc in follow up messages on the mailing list thread. (Phoronix tests will be conducted soon.)

LZ4 is designed to be "a very fast lossless compression algorithm, providing compression speed at 300 MB/s per core, scalable with multi-cores CPU. It also features an extremely fast decoder, with speeds up and beyond 1GB/s per core, typically reaching RAM speed limits on multi-core systems." Additional details on LZ4 compression are available from its Google Code page.

Assuming all goes well, the LZ4 support for Btrfs compression could make it into the Linux 3.4 kernel with the Snappy support. Let's just hope that separately the Btrfs fsck tool becomes available well ahead of Linux 3.4.