On Thu, Mar 28, 2013 at 07:41:55AM -0700, Sage Weil wrote: > 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. Oh, I didn't know about that ! Any chance of submitting it to the main Samba repository so we can keep it up to date with VFS changes ? Jeremy. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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