At Fri, 21 May 2010 06:28:42 +0100, Stefan Hajnoczi wrote: > > On Thu, May 20, 2010 at 11:16 PM, Christian Brunner <chb@xxxxxx> wrote: > > 2010/5/20 Anthony Liguori <anthony@xxxxxxxxxxxxx>: > >> Both sheepdog and ceph ultimately transmit I/O over a socket to a central > >> daemon, right? So could we not standardize a protocol for this that both > >> sheepdog and ceph could implement? > > > > There is no central daemon. The concept is that they talk to many > > storage nodes at the same time. Data is distributed and replicated > > over many nodes in the network. The mechanism to do this is quite > > complex. I don't know about sheepdog, but in Ceph this is called RADOS > > (reliable autonomic distributed object store). Sheepdog and Ceph may > > look similar, but this is where they act different. I don't think that > > it would be possible to implement a common protocol. > > I believe Sheepdog has a local daemon on each node. The QEMU storage > backend talks to the daemon on the same node, which then does the real > network communication with the rest of the distributed storage system. Yes. It is because Sheepdog doesn't have a configuration about cluster membership as I mentioned in another mail, so the drvier doesn't know which node to access other than localhost. > So I think we're not talking about a network protocol here, we're > talking about a common interface that can be used by QEMU and other > programs to take advantage of Ceph, Sheepdog, etc services available > on the local node. > > Haven't looked into your patch enough yet, but does librados talk > directly over the network or does it connect to a local daemon/driver? > AFAIK, librados access directly over the network, so I think it is difficult to define a common interface. Thanks, Kazutaka -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
