On Tue, Jul 14, 2015 at 4:11 AM, Kent Overstreet
[off-list ref] wrote:

On Tue, Jul 14, 2015 at 09:05:39AM +0300, Vasiliy Tolstov wrote:

quoted

Does it support discards?

quoted

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.

Ok, I am really confused right now. So, the format utility still
allows -B (backing device). Is it just an artifact left over after
block caching? Because I could not make it work. Any thread
encountering  the formatted backing device just hangs inside the
kernel space until reboot. Is there something wrong with my setup or
backing devices are just an illusion, a figment of kernel's
imagination? And, if not, how do they relate to tiers?
Could you give a simple example of a usual setup - one small and fast
SSD and huge but slow RAID-6? Should I now format both partitions as
-C and assign tier 1 to RAID-6?

quoted

14 июля 2015 г. 3:58 пользователь "Kent Overstreet" <
kent.overstreet@gmail.com> написал:

quoted

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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Denis