Thank you, Mike. The reason why I like block device is that it has the best reading performance. But not being able to be shared is a fatal drawback here. Maybe I should change some strategy or tuning the ceph fs. My goal is to use a cluster to host a lot of small images, each of which is about 17KB.
On Wed, May 1, 2013 at 11:31 AM, Mike Lowe <j.michael.l...@gmail.com> wrote: > That is the expected behavior. RBD is emulating a real device, you > wouldn't expect good things to happen if you were to plug the same drive > into two different machines at once (perhaps with some soldering). There > is no built in mechanism for two machines to access the same block device > concurrently, you would need to add a bunch of extra stuff in the same way > that ocfs or gfs has. CephFS on the other hand is a parallel filesystem > designed for multiple concurrent client access and does have such > mechanisms (with limits, read the docs). > > On May 1, 2013, at 11:19 AM, Yudong Guang <guangyudongb...@gmail.com> > wrote: > > > Hi, > > > > I've been trying to use block device recently. I have a running cluster > with 2 machines and 3 OSDs. > > > > On a client machine, let's say A, I created a rbd image using `rbd > create` , then formatted, mounted and wrote something in it, everything was > working fine. > > > > However, problem occurred when I tried to use this image on the other > client, let's say B, on which I mapped the same image that created on A. I > found that any changes I made on any of them cannot be shown on the other > client, but if I unmap the device and then map again, the changes will be > shown. > > > > I tested the same thing with ceph fs, but there was no such problem. > Every change made on one client can be shown on the other client instantly. > > > > I wonder whether this kind of behavior of RADOS block device is normal > or not. Is there any way that we can read and write on the same image on > multiple clients? > > > > Any idea is appreciated. > > > > Thanks > > _______________________________________________ > > ceph-users mailing list > > ceph-users@lists.ceph.com > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > -- Yudong Guang guangyudongb...@gmail.com 786-554-3993 +86-138-1174-5701
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