Open Stack

On 15 May 2013 06:22, John Griffith <john.griffith at solidfire.com> wrote:

> What I had in mind for Cinder, was the addition of of a property/column in
> the Volume object.  This would be a Read Only flag.  The use case here would
> be that a tenant could take a volume that they've populated with data and
> set it to R/O explicitly.  This would mean providing an API call to enabled
> setting and clearing of this flag of course.

This seems like a useful feature

> In addition, I'd like to modify the cinder attach code, so that if for
> example a volume is "in use" attached to an instance, and a subsequent
> attach was requested, rather than failing stating that the volume must be
> available, we allow the attach however set it as Read Only.  This would be
> the default behavior, if we get to a point where we are interested in
> multiple attach R/W (which is quite frankly rather scary to me) I would
> propose that there explicit settings a user must request to do this and that
> it's done via extension or disabled by default via the cinder.conf file.

I think that doing a read-only attach rather than failing the attach
by default is a /really/ bad idea... for most filesystems, that mount
is going to be entirely useless if there is a R/W mount in existance,
and it is going to lead to read corruption in surprising ways. The
current behaviour is far in preference to that.

Any form of multi-attach should only happen if specifically requested,
and come with 'here be dragons' warnings...


--
Duncan Thomas