This doesn't sound quite right but I'm not sure if the problem is a terminology disconnect or a concept one. Let's go through them On Fri, Mar 1, 2013 at 3:08 PM, McNamara, Bradley <Bradley.McNamara@xxxxxxxxxxx> wrote: > I'm new, too, and I guess I just need a little clarification on Greg's statement. The RBD filesystem > is mounted to multiple VM servers By "RBD filesystem" do you mean an RBD image of probably between 10GB and 2TB? Or do you mean that each VM server is talking to the Ceph cluster? The former definition would be a "no, don't do that", the second is "of course". >, say, in a Proxmox cluster, and as long as any one VM image file on that filesystem is only being accessed from one node of the cluster, > everything will work, and that's the way shared storage is intended to work within Ceph/RBD. Correct? > > I can understand things blowing up if the same VM image file is being accessed from multiple nodes in the cluster, and that's where a clustered filesystem comes into play. By "VM image file" do you mean an rbd image, or are you actually talking about a single RBD volume, formatted to use ext4, hosting 10 different VM images? > I guess in my mind/world I was envisioning a group of VM servers using one large RBD volume, that is mounted to each VM server in the group, to store the VM images for all the VM's in the group of VM servers. This way the VM's could migrate to any VM server in the group using the RBD volume. So an "RBD volume" in the Ceph project is equivalent to a single logical SATA disk. Those volumes are stored in "RADOS pools", which for the purpose of this conversation is the collection of physical hardware you are aggregating into a Ceph cluster. You can mount the RBD volume from however many servers you like at a time, but if you do so you'd better be careful about cache flushes etc! A more likely management setup would be to mount each volume to one server at a time, and then if you need to migrate the VM to a different host you attach it on-demand. -Greg _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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