On Wed, 27 Mar 2013, Matthieu Patou wrote: > On 03/27/2013 10:41 AM, Marco Aroldi wrote: > > Hi list, > > I'm trying to create a active/active Samba cluster on top of Cephfs > > I would ask if Ceph fully supports CTDB at this time. > > If I'm not wrong Ceph (even CephFS) do not support exporting a block device or > mounting the same FS more than once whereas CTDB explicitly require that you > have a distributed filesystem where the same filesystem is mounted across all > the nodes. Er, sort of. RBD presents a block-based interface. As many clients as you want can use that at the same time, although the client caching should be disabled if the users don't call flush() to make their writes visible to others. Beyond that, RBD itself doesn't care how many people use it. *However*, if you put a "local file system" on top of RBD (like ext4, xfs, btrfs, zfs, ...), only one client should use RBD at a time because those file systems are designed for exclusive access to the disk. If you use a "clustered file system" like ocfs2 or gfs[2], multiple clients can share the same RBD volume in a useful way, but they expect coherency to behave like on a SAN (which means writes are visible immediately but not durable until flush), which means RBD caching should be turned off. CephFS is designed for concurrent, shared, coherent access from many many clients. Think NFS, but scalable, and coherent/consistent when clients are accessing the same files and directories. As for CTDB: we haven't looked at this specifically in the context for Samba. Generally speaking, anything you can do with NFS or another shared file system you can do with CephFS. IIRC last time I discussed this with the Samba guys, there is more we could do here to make CTDB much more efficient (by backing it with RADOS, for example), but we haven't looked at any of this carefully. We would love to see clustered Samba working well on CephFS, though! If you haven't already, plese look at our samba.git cloen on github, which has patches gluing libcephfs directly into Samba's VFS, allowing you to directly reexport CephFS via Samba without a local mountpoint in the middle. sage _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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