From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1N1MpL-0007ef-0K for qemu-devel@nongnu.org; Fri, 23 Oct 2009 12:17:19 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1N1MpG-0007cQ-2E for qemu-devel@nongnu.org; Fri, 23 Oct 2009 12:17:18 -0400 Received: from [199.232.76.173] (port=46443 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1N1MpF-0007cK-TZ for qemu-devel@nongnu.org; Fri, 23 Oct 2009 12:17:13 -0400 Received: from mail-yx0-f188.google.com ([209.85.210.188]:46710) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1N1MpF-0000Xb-Jo for qemu-devel@nongnu.org; Fri, 23 Oct 2009 12:17:13 -0400 Received: by yxe26 with SMTP id 26so7637129yxe.4 for ; Fri, 23 Oct 2009 09:17:13 -0700 (PDT) MIME-Version: 1.0 Sender: morita.kazutaka@gmail.com In-Reply-To: References: <4ADE988B.2070303@lab.ntt.co.jp> <4AE07A7F.8000002@redhat.com> <8fd1d76d0910230341w7978ac09te203ef34b79a86c6@mail.gmail.com> Date: Sat, 24 Oct 2009 01:17:12 +0900 Message-ID: <8fd1d76d0910230917p565d5738i151300db9d58c674@mail.gmail.com> Subject: Re: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM From: MORITA Kazutaka Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: linux-fsdevel@vger.kernel.org, Avi Kivity , kvm@vger.kernel.org, qemu-devel@nongnu.org On Fri, Oct 23, 2009 at 8:10 PM, Alexander Graf wrote: > > On 23.10.2009, at 12:41, MORITA Kazutaka wrote: > > On Fri, Oct 23, 2009 at 12:30 AM, Avi Kivity wrote: > > How is load balancing implemented? =A0Can you move an image transparently > > while a guest is running? =A0Will an image be moved closer to its guest? > > Sheepdog uses consistent hashing to decide where objects store; I/O > load is balanced across the nodes. When a new node is added or the > existing node is removed, the hash table changes and the data > automatically and transparently are moved over nodes. > > We plan to implement a mechanism to distribute the data not randomly > but intelligently; we could use machine load, the locations of VMs, etc. > > What exactly does balanced mean? Can it cope with individual nodes having > more disk space than others? I mean objects are uniformly distributed over the nodes by the hash functio= n. Distribution using free disk space information is one of TODOs. > Do you support multiple guests accessing the same image? > > A VM image can be attached to any VMs but one VM at a time; multiple > running VMs cannot access to the same VM image. > > What about read-only access? Imagine you'd have 5 kvm instances each > accessing it using -snapshot. By creating new clone images from existing snapshot image, you can do the similar thing. Sheepdog can create cloning image instantly. --=20 MORITA, Kazutaka NTT Cyber Space Labs OSS Computing Project Kernel Group E-mail: morita.kazutaka@lab.ntt.co.jp