Number of faults a system can withstand without repairs

We consider the following scheduling problem. A system is composed of n processors drawn from a pool of N. The processors can become faulty while in operation and faulty processors never recover. A report is issued whenever a fault occurs. This report states only the existence of a fault, but does not indicate its location. Based on this report, the scheduler can reconngure the system and choose another set of n processors. The system operates satisfactorily as long as at most f of the n selected processors are faulty. We exhibit a scheduling strategy allowing the system to operate satisfactorily until approximately (N=n)f faults are reported in the worst case. Our precise bound is tight.