Re: [ANNOUNCE] bcachefs!

Kent Overstreet
2015-07-14T08:11:09Z

On Tue, Jul 14, 2015 at 09:05:39AM +0300, Vasiliy Tolstov wrote:
> Does it support discards?

Yes

> Does this announce means that bcache block device
> no longer maintained by developers?

There's no plural, it's just me :)

I've been overly stressed and burned out from a startup gone horribly wrong -
I'm going to try to start doing some maintainence of upstream bcache again once
I've moved.

I apologize for my absence on the list these past months, I've had (and still
have) entirely too much to juggle - hint hint, if anyone wants to jump in and
help out.

> What about performance tests with compared to plain btrfs/ext4?

I haven't done much comparison benchmarking yet, I'll post them once I have. If
anyone else wants to do some benchmarking I'd love to see the results.

(From the testing I have done - untarring the kernel (on a fast device, with the
tar file already uncompressed and in kernel so we're purely cpu bound) -
bcachefs is equal to ext4 to within the margin of error. On dbench when we're
purely cpu bound, bcachefs is roughly 30% off from ext4. I think the majority of
that is bcachefs's dirent code being somewhat cpu heavy).

The long term goal is to be at least as fast on ext4/xfs for any given workload,
and on typical workloads we ought to be faster - and in particular bcachefs
should have better and more predictable latency, due to the way journalling
works.

> Format command have one device, how provide tiering?

--tier specifies the tier of the devices that come after it, where the smaller
index is the faster tier.

Only tiers 0 and 1 are supported for now, that will be increased whenever
someone gets around to it.

If /dev/sda is your fast device and /dev/sdb is your slow device, run

# bcacheadm format -C /dev/sda --tier 1 /dev/sdb

bcacheadm format --help gives you the full list of options.

> 14 июля 2015 г. 3:58 пользователь "Kent Overstreet" <
> kent.overstreet@gmail.com> написал:
>
> > Short announcement, because I'm in the process of moving - but I wanted to
> > get
> > this out there because the code is up and I think it's reasonably stable
> > right
> > now.
> >
> > Bcachefs is a posix filesystem that I've been working towards for - well,
> > quite
> > awhile now: it's intended as a competitor/replacement for ext4/xfs/btrfs.
> >
> > Current features
> > - multiple devices
> > - replication
> > - tiering
> > - data checksumming and compression (zlib only; also the code doesn't
> > work with
> > tiering yet)
> > - most of the normal posix fs features (no fallocate or quotas yet)
> >
> > Planned features:
> > - snapshots!
> > - erasure coding
> > - more
> >
> > There will be a longer announcement on LKML/linux-fs in the near future
> > (after
> > I'm finished moving) - but I'd like to get it a bit more testing from a
> > wider
> > audience first, if possible.
> >
> > You need the bcache-dev branch, and the new bcache tools - be warned, this
> > code
> > is _not_ compatible with the upstream bcache on disk format:
> >
> > $ git clone -b bcache-dev http://evilpiepirate.org/git/linux-bcache.git
> > $ git clone -b dev http://evilpiepirate.org/git/bcache-tools.git
> >
> > Then do the usual compiling...
> >
> > # bcacheadm format -C /dev/sda1
> > # mount /dev/sda1 /mnt
> >
> > The usual caveats apply - it might eat your data, the on disk format has
> > _not_
> > been stabilized yet, etc. But it's been reasonably stable for me, and
> > passes all
> > but 2-3 of the supported xfstests.
> >
> > Try it out and let me know how it goes!
> >
> > Also, programmers please check out the bcache guide - feedback is
> > appreciated:
> >
> > http://bcache.evilpiepirate.org/BcacheGuide/
> >
> > Thanks!
> > --
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