RAID 1 with backup availability
A RAID 1 in a very critical environment is composed by two disks that mirror the same data. On the average, every MTTF = 100 days, one of the disks fails. In this case, recovery consist in replacing the broken disk, reconstruct the data, and return to normal operation. This requires an average of MTTR = 5 days. Should also the second disk fail during the recovery stage, the system will go in a fault state, where to be restored, it will require a total reconstruction of the system from the backup. This will take an average 15 days.
Considering all failure and recovery time distribution exponential, and the system starts in a state where both disks are working:
• Draw the Markov Chain of the model
• Compute the infinitesimal generator and solve the corresponding differential equations
• Show the probability of the various states for the time T = [0, 10000] days
