From mboxrd@z Thu Jan 1 00:00:00 1970 From: MORITA Kazutaka Subject: Re: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM Date: Sat, 24 Oct 2009 01:17:12 +0900 Message-ID: <8fd1d76d0910230917p565d5738i151300db9d58c674@mail.gmail.com> References: <4ADE988B.2070303@lab.ntt.co.jp> <4AE07A7F.8000002@redhat.com> <8fd1d76d0910230341w7978ac09te203ef34b79a86c6@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-fsdevel@vger.kernel.org, Avi Kivity , kvm@vger.kernel.org, qemu-devel@nongnu.org To: Alexander Graf Return-path: In-Reply-To: Sender: kvm-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.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 transpare= ntly > > while a guest is running? =A0Will an image be moved closer to its gue= st? > > 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, e= tc. > > What exactly does balanced mean? Can it cope with individual nodes ha= ving > more disk space than others? I mean objects are uniformly distributed over the nodes by the hash fun= ction. 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