BTRFS: The Good, The Bad and The Ugly

[Manuel Escudero]

Today I'll be switching from BTRFS to Ext4 again because of the troubles
I've been having with
the New Linux Filesystem. As BTRFS is going to be the Default in F16 I
wanted the developers to
know what kind of troubles I've been experiencing with this FS in F15 so
they can take a look
at them in order to have a better F16 release:

The Good:

Since BTRFS arrived into my computer (Everything in the HDD is formated with
BTRFS excluding "/boot")
I've seen a performance improvement in the data transfer part from and to
the computer (copying files seem to
be faster than before) But that's all about the good things I noticed...

The Bad:

BTRFS has reduced system's overall performance, at this point, sometimes it
is OK, sometimes it is
VERY BAD, I've noticed "Performance Peaks" in F15 with BTRFS and the Boot
times are not nice: I mean,
they are not the slowest ones, but they're not as good as Before in F14 with
Ext4 instead of BTRFS.

The performance Running/Launching apps has been afected too and now the PC
freezes sometimes (that never
happened in F14 unless I forced it a lot with 4 VM's to suck the 4GB of RAM
I have); And Now it freezes
very often when it wants without a lot of effort.

The Ugly:

Running VM's when having their virtual HDD's stored in a BTRFS partition is
DEATH!
They're very slow, sometimes they open, sometimes they not, usually they
freeze, You can't
work with them. Same thing about Gnome Shell working over a BTRFS partition:
it is really slow,
sometimes it reacts but most of the time is pretty unresponsive.

Reading in the Web, I found that some users think that the BTRFS poor
performance is caused by some
special kind of fragmentation it suffers, others think it's because of it's
CopyonWrite attributes and some
others blame other stuff, God Knows! the only thing I know is that BTRFS is
not ready for being
used in normal production machines (as I tought) and it needs to be fixed
before the release of F16, because it's
performance is really far from good...

Other Stuff I noticed is that with Kernel 2.6.38.8-35 the system seems to
work better that with the previous one,
just a little, but is some kind of improvement.

Here you have all the info I found on the net about BTRFS Performance
issues noticed by users:

https://bugzilla.redhat.com/show_bug.cgi?id=689127

http://arosenfeld.wordpress.com/2010/12/27/back-to-ext4-from-btrfs/

http://www.vyatta4people.org/btrfs-is-a-bad-choice-when-running-kvm/

http://lkml.org/lkml/2010/7/13/475

http://blog.patshead.com/2011/03/btrfs---six-months-later.html

I only have a question:

Why Any Kind of VM is Sooo Slow when being stored on a BTRFS
partition? Any Way to Solve this? or at least have a BTRFS performance
improvement?

Thanks! Hope this mail help the Developers improving the new FS.

Have a Nice Day!

-- 
Manuel Escudero
Linux User #509052
Twitter: @Jmlevick <http://twitter.com/Jmlevick>
Blogger: Blog Xenode <http://xenodesystems.blogspot.com/>
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