I think shared persistent volumes are a great feature addition! Couple things that need to be addressed
--> Who gets charged for the shared disk quota if multiple tasks share them? I'm assuming the one who creates a RW copy? --> How does the resource handling logic work in Mesos if a resource is re-offered while still in use? I think this is the piece that needs some major thinking. It's worthwhile to start a design doc around this. Anindya, are you up for the task? Thanks, On Mon, Sep 21, 2015 at 11:00 AM, Anindya Sinha <anindya.si...@gmail.com> wrote: > Now that mesos has introduced support for persistent volumes, the > persistent volumes that are created on a specific slave is offered to the > framework(s) as another resource. As a result, a task which needs RW access > to that persistent volume can use that resource. > > Till this task is running, that persistent volume cannot be offered to the > framework(s) and hence would not be available for another task running on > the same agent. > > Let us consider an use case wherein a service needs access to the same > persistent volume from multiple task instances running on the same agent > simultaneously, ie. when both (or multiple) of such task instances are > RUNNING. Since the persistent volume is not offered as a resource to the > framework(s) till a task that has grabbed it is still active, the > subsequent instances needed access to the same persistent volume is not > feasible. > > To alleviate that scenario, we propose making persistent volumes "sharable" > (as optional). Default behavior can still be "non-sharable" but frameworks > may want to CREATE persistent volumes as "sharable" (which would need an > optional field in Resources.DiskInfo.Persistence). Hence, we would allow > "sharable" persistent volumes be offered as resources to the framework(s) > [matching role] even if it has been grabbed by a task already running on > the agent, so as that subsequent tasks can use that persistent volume. > > Comments/concerns? > > Thanks > > Anindya >
