From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tommi Virtanen Subject: Re: Poor read performance in KVM Date: Fri, 20 Jul 2012 09:42:29 -0700 Message-ID: References: <5002C215.108@bashkirtsev.com> <5003B1CC.4060909@inktank.com> <50064DCD.8040904@bashkirtsev.com> <5006D5FB.8030700@inktank.com> <50080D9D.8010306@bashkirtsev.com> <50085518.80507@inktank.com> <500984AC.9030104@bashkirtsev.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-pb0-f46.google.com ([209.85.160.46]:63153 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752348Ab2GTQmu (ORCPT ); Fri, 20 Jul 2012 12:42:50 -0400 Received: by pbbrp8 with SMTP id rp8so6397322pbb.19 for ; Fri, 20 Jul 2012 09:42:50 -0700 (PDT) In-Reply-To: <500984AC.9030104@bashkirtsev.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Vladimir Bashkirtsev Cc: Josh Durgin , ceph-devel On Fri, Jul 20, 2012 at 9:17 AM, Vladimir Bashkirtsev wrote: > not running. So I ended up rebooting hosts and that's where fun begin: btrfs > has failed to umount , on boot up it spit out "btrfs: free space inode > generation (0) did not match free space cache generation (177431)". I have > not started ceph and made an attempt to umount and umount just froze. > Another reboot: same stuff. I have rebooted second host and it came back > with the same error. So in effect I was unable to mount btrfs and read it: > no wonder that ceph was unable to run. Actually according to mons ceph was The btrfs developers tend to be good about bug reports that severe -- I think you should email that mailing list and ask if that sounds like known bug, and ask what information you should capture if it happens again (assuming the workload is complex enough that you can't easily capture/reproduce all of that). > But it leaves me with very final question: should we rely on btrfs at this > point given it is having such major faults? What if I will use well tested > by time ext4? You might want to try xfs. We hear/see problems with all three, but xfs currently seems to have the best long-term performance and reliability. I'm not sure if anyone's run detailed tests with ext4 after the xattrs-in-leveldb feature; before that, we ran into fs limitations.