Open Stack

On 05/18/2013 03:14 PM, Duncan Thomas wrote:
> 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...
I agree with this as well.   I think it's a bad idea to default to read 
only.
It's a safer bet to only do read only mount if requested.

Walt