From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n2GLakIe004543 for ; Mon, 16 Mar 2009 17:36:46 -0400 Received: from mail-qy0-f103.google.com (mail-qy0-f103.google.com [209.85.221.103]) by mx3.redhat.com (8.13.8/8.13.8) with ESMTP id n2GLaS7O001105 for ; Mon, 16 Mar 2009 17:36:28 -0400 Received: by qyk1 with SMTP id 1so1378080qyk.23 for ; Mon, 16 Mar 2009 14:36:28 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <49BEC1CC.5050900@gmail.com> References: <49BA9BF9.3070507@esiway.net> <7B7881568CF40E4388B615CD06F87B98098BDA@clara.maurer-it.com> <49BC511E.5040402@esiway.net> <49BE9F73.8050109@gmail.com> <87f94c370903161236y197edd7ehef3dc8eefc6d617b@mail.gmail.com> <49BEB683.7020209@gmail.com> <87f94c370903161354v2e43f13ci914f45175ca6af6f@mail.gmail.com> <49BEC1CC.5050900@gmail.com> Date: Mon, 16 Mar 2009 17:36:27 -0400 Message-ID: <87f94c370903161436y40eddb3pe162bfa64a90e371@mail.gmail.com> Subject: Re: [linux-lvm] fsync() and LVM From: Greg Freemyer Content-Transfer-Encoding: 8bit Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="utf-8" To: LVM general discussion and development On Mon, Mar 16, 2009 at 5:17 PM, Les Mikesell wrote: > Greg Freemyer wrote: >> >>>> Those are some very significant subsystems. �I have to believe >>>> filesystems have another way to implement fsync if barriers are not >>>> supported in the stack of block susbsystems. >>> >>> If you can't get the completion status from the underlying layer, how can >>> a >>> filesystem possibly implement it? >> >> Barriers is a specific technology and they were just implemented in >> linux around 2005 I think. �(see documentation/barriers.txt) >> >> Surely there was a mechanism in place before that. > > I'm not sure that's a reasonable assumption. > >>>> Maybe this discussion needs to move to a filesystem list, since it is >>>> the filesystem that is responsible for making fsync() work even in the >>>> absence of barriers. >>> >>> I though linux ended up doing a sync of the entire outstanding buffered >>> data >>> for a partition with horrible performance, at least on ext3. >> >> Yes, I understand fsync is horribly slow in ext3 and that may be the >> reason. �Supposedly much better in ext4. �Still if a userspace app >> calls fsync and in turn the filesystem does something really slow due >> to the lack of barriers, then this conversation should be about the >> poor performance of fsync() when using lvm (or mdraid, or drdb), not >> the total lack of fsync() support. > > I haven't seen anyone claim yet that there is support for fsync(), which > must return the status of the completion of the operation to the > application. �If it does, then the discussion could turn to performance. > > -- > �Les Mikesell > � lesmikesell@gmail.com Is your specific interest to ext3? If so, I suggest you post a question there along the lines of: Device Mapper does not support barriers if more than one physical device is in use by the LV. If I'm using ext3 on a LV and I call fsync() from user space, how is fsync() implemented. Or is it not? The ext4 list is . I see some ext3 stuff posted there, or it may have its own list. Greg -- Greg Freemyer Head of EDD Tape Extraction and Processing team Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer First 99 Days Litigation White Paper - http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com