2. Select Tool for Reliability

Consider the following system with disks 1,2 and 3.

-- 10 Disk 1s with 1,000,000-hour MTTF

-- 19 Disk 2s with 450,000-hour MTTF

-- 1 Disk 3s with 700,000-hour MTTF

-- MTTR for single disk is 8000 hours and 13,000 hours for the system

-- p(disk) is 1

(a) Find the MTTF of the system.

(b) Use the MTTF found above, to find the Reliability and MTTDL. Which RAID level is best for each failure characteristic.

MTTDL RAID5 P+Q

Double/Triple Disk Failure

System Crash + Disk Failure

Single/Double Failure + Bit Error

MTTDL	RAID5	P + Q
Double/Triple Disk Failure
System Crash + Disk Failure
Single/Double Failure + Bit Error

(c) Define the availability of a system based on its MTTF and MTTR?

(d) What is the relation between system failure rate and MTTF?