1. A system, comprising: one or more processors; and logic encoded in one or more tangible media for execution by the one or more processors and when executed operable to perform operations comprising: assigning a virtual operating system container from any of a reserve zone pool and a non-reserve zone pool to a task group, the task group comprising a set of tasks for a phase of a request, the phase comprising any of map or reduce; and executing the set of tasks within the assigned virtual operating system container.