Open Stack

On 06/10/2014 09:57 PM, Janczuk, Tomasz wrote:
> Using processes to isolate tenants is certainly possible. There is a range
> of isolation mechanisms that can be used, from VM level isolation
> (basically a separate deployment of the broker per-tenant), to process
> level isolation, to sub-process isolation. The higher the density the
> lower the overall marginal cost of adding a tenant to the system, and
> overall cost of operating it. From the cost perspective it is therefore
> desired to provide sub-process multi-tenancy mechanism; at the same time
> this is the most challenging approach.

Where does the increased cost for process level isolation come from? Is
it simply the extra process required (implying an eventual limit for a
given VM)?

With sub-process isolation you have to consider the fairness of
scheduling between operations for different tenants, i.e. potentially
limiting the processing done on behalf of any given tenant in a given
period. You would also need to limit the memory used on behalf of any
given tenant. Wouldn't you end up reinventing much of what the operating
system does?