On 03/28/2013 07:41 AM, 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.
Ok my bad, I misunderstood, the documentation of Cephfs was not super
clear on this point I assumed that if it wasn't stated then it means
that multiple coherent client access wasn't a feature.
Matthieu.
_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
