SLIDE 1
Evaluate the reliability and the availability of a system composed of three CPUs (working in parallel and whose output is given by a voter), a RAID 1 storage system with 4+4 disks three buses (working in parallel and whose outputs are given by voters), one keyboard, one printer and one monitor. Assume that faults are exponentially distributed with rates equal to , , , , , , . The repair rate is equal for all components. Subsystems: SUBCPU , SUBBUS, SUBDISK, SUBPRI, SUBKEY and SUBMON (SUBCPU and SUBBUS include voters).
Reliability:
Serial interconnections: ∏ Thus: Reliability of a generic component i:
Availability:
∏
CPU CPU V CPU MONITOR PRINTER KEYBOARD RAID 1 V V V V
SLIDE 2
Availability of a generic component i: where
and
Reliability and availability of subsystems
SUBCPU system. = [ ] [
]
where : : reliability of the CPU ; : reliability of the VOTER-CPU ; : availability of the CPU; : availability of the VOTER-CPU . SUBBUS BUS: interconnection. = [ ] [
]
where : : reliability of a BUS ; : reliability of a VOTER- BUS; : availability of a BUS; : availability of a VOTER- BUS; SUBDISK RAID 1 where :
SLIDE 3
: reliability of disk couple; : availability of disk couple; Reliability of a disk couple: ( ) Availability of a disk couple: SUBPRI where : : reliability of the printer; : availability of the printer; SUBKEY where : : reliability of the keyboard ; : availability of the keyboard. SUBMON where : : reliability of the monitor; : availability of the monitor.
