lkml.org 
[lkml]   [2010]   [Jul]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: BTRFS: Unbelievably slow with kvm/qemu
From
On Tue, Jul 13, 2010 at 6:29 AM, Avi Kivity <avi@redhat.com> wrote:
> Btrfs is very slow on sync writes:
>
> 45KB/s, while 4-5MB/s traffic was actually going to the disk.  For every 4KB
> that the the application writes, 400KB+ of metadata is written.
>
> (It's actually worse, since it starts faster than the average and ends up
> slower than the average).
>
> For kvm, you can try cache=writeback or cache=unsafe and get better
> performance (though still slower than ext*).
>
Yeah, well I've already moved the virtual hd file to an ext3
partition, so the problem for me was actually already "solved" before
posting the first post. I posted the first message just to report the
particularly bad performances of Btrfs for this test-case, so that, if
not already known, they could be investigated and hopefully solved.

By the way, thanks to everyone who answered!

--
Giangiacomo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2010-07-14 04:41    [W:0.084 / U:1.964 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site