On Mon, May 27, 2019, 5:33 PM Martinx - ジェームズ <thiagocmartinsc@gmail.com> wrote:

Hello,

I'm very curious about this as well!

It would be awesome to support Cinder multi-attach when using Ceph... If the code is already there, how to use it?!

Cheers,
Thiago
On Mon, 27 May 2019 at 03:52, Bernd Bausch <berndbausch@gmail.com> wrote:
The Stein release notes mention that the RBD driver now supports multiattach, but i have not found any details. Are there limitations? Is there a need to configure anything?

In the RBD driver, I find this:
    def _enable_multiattach(self, volume):
        multipath_feature_exclusions = [
            self.rbd.RBD_FEATURE_JOURNALING,
            self.rbd.RBD_FEATURE_FAST_DIFF,
            self.rbd.RBD_FEATURE_OBJECT_MAP,
            self.rbd.RBD_FEATURE_EXCLUSIVE_LOCK,
        ]
This seems to mean that journaling and other features (to me, it's not quite clear what they are) will be automatically disabled when switching on multiattachment.

Further down in the code I see that replication and multiattach are mutually exclusive.

Is there some documentation about the Ceph multiattach feature, even an email thread?

Thanks,

Bernd

There isn't really a Ceph multi-attach feature using Cinder. The code comment is stating that, while the Openstack side of things is in place, Ceph doesn't yet support it with RBD due to replication issues with multiple clients. The Ceph community is aware of it, but has thus far focused on CephFS as the shared file system instead.

This could possibly be used with the NFS Cinder driver talking to Ganesha with CephFS mounted. You may also want to look at Openstack's Manilla project to orchestrate that.

-Erik