Reliability: Serial interconnections: Thus: Reliability of a - PDF document

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. CPU CPU CPU KEYBOARD MONITOR PRINTER RAID 1 V V V V V Subsystems: SUB CPU , SUB BUS , SUB DISK , SUB PRI , SUB KEY and SUB MON ( SUB CPU and SUB BUS include voters). Reliability: Serial interconnections: ∏ Thus: Reliability of a generic component i : Availability: ∏

Availability of a generic component i : where and Reliability and a vailability of subsystems SUB CPU system . = [ ] ] [ where : : reliability of the CPU ; : reliability of the VOTER-CPU ; : availability of the CPU; : availability of the VOTER-CPU . SUB BUS BUS: interconnection. = [ ] ] [ where : : reliability of a BUS ; : reliability of a VOTER- BUS; : availability of a BUS; : availability of a VOTER- BUS; SUB DISK  RAID 1 where :

: reliability of disk couple; : availability of disk couple; Reliability of a disk couple: ( ) Availability of a disk couple: SUB PRI where : : reliability of the printer; : availability of the printer; SUB KEY where : : reliability of the keyboard ; : availability of the keyboard. SUB MON where : : reliability of the monitor; : availability of the monitor.