New Linux filesystem: bcachefs

jeremy · 08-21-2015, 11:33 AM

Quote:

From Kent Overstreet <>
Subject [ANNOUNCE] bcachefs - a general purpose COW filesystem

For those who haven't kept up with bcache, the bcache codebase has been
evolving/metastasizing into a full blown, general purpose posix filesystem - a
modern COW filesystem with checksumming, compression, multiple devices, caching,
and eventually snapshots and all kinds of other nifty features.

"Yet another new filesystem? Why?"

Well, years ago (going back to when I was still at Google), I and the other
people working on bcache realized that what we were working on was, almost by
accident, a good chunk of the functionality of a full blown filesystem - and
there was a really clean and elegant design to be had there if we took it and
ran with it. And a fast one - the main goal of bcachefs to match ext4 and xfs on
performance and reliability, but with the features of btrfs/zfs.

It's taken a long time to get to this point - longer than I would have guessed
if you'd asked me back when we first started talking about it - but I'm pretty
damn proud of where it's at now.

CURRENT STATUS:

It's more or less feature complete - nothing critical should be missing. You can
try it out and play with it now, and I need more testers/users trying it out and
finding issues. It's in the bcache-dev branch, and you need the dev branch of
bcache-tools:

http://evilpiepirate.org/git/linux-bcache.git bcache-dev
http://evilpiepirate.org/git/bcache-tools.git dev

# bcacheadm format -C /dev/sda1
# mount -t bcache /dev/sda1 /mnt

(one annoyance: blkid recognizes the superblock when bcacheadm formats it, but
usually not after the first mount because it grows to over 4k after allocating
the journal, so after the first mount you need the -t bcache)

I've been focusing on stability and correctness for quite awhile now; xfstests
passes aside from a few relatively minor known issues. It probably won't eat
your data - but no promises.

Also note - the on disk format is NOT finalized yet, and won't be for awhile
though changes are infrequent at this point.

User documentation is still pretty sparse, but one thing I do want people to
look at is the internals documentation:
http://bcache.evilpiepirate.org/BcacheGuide/

More at LKML...

Have any LQ members used bcachefs?

--jeremy

ugjka · 08-21-2015, 12:19 PM

I like this feature

Quote:

caching/tiering (naturally)
you can format multiple devices at the same time with bcacheadm, and assign
them to different tiers - right now only two tiers are supported, tier 0
(default) is the fast tier and tier 1 is the slow tier. It'll effectively do
writeback caching between tiers.