On Mon, 2013-05-13 at 18:55 +0200, Gregory Farnum wrote: > On Mon, May 13, 2013 at 9:10 AM, Harald Rößler <Harald.Roessler@xxxxxx> wrote: > > > > Hi Together > > > > is there a description of how a shared image works in detail? Can such > > an image can be used for a shared file system on two virtual machine > > (KVM) to mount. In my case, write on one machine and read only on the > > other KVM.Are the changes are visible on the read only KVM? > > The image is just striped across RADOS objects. In general you can > think of it behaving exactly like a hard drive connected to your > computer over iSCSI — a proper shared FS (eg, OCFS2) will work on top > of it, but there's no magic that makes running an ext4 mount on two > machines work... > -Greg > Software Engineer #42 @ http://inktank.com | http://ceph.com Hi Greg Thanks, and sorry maybe I did not explain clearly what I mean or. When I' mounting a rbd image on two KVM machines, then if I am writing a file in one system the other system does not recognize the change of the file system. I thought there is some magic in librbd which give the OS the information that something have changed, like when I am mounting a NFS share. I saw in the documentation the "--shared tag" : Option for lock add that allows multiple clients to lock the same image if they use the same tag. The tag is an arbitrary string. This is useful for situations where an image must be open from more than one client at once, like during live migration of a virtual machine, or for use underneath a clustered file system. The use case is multiply KVM systems are mounting the same data storage, without use of cephfs (MDS). Thanks Harry ��.n��������+%������w��{.n����z��u���ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
