Mastering EJB3 Chapter 19(Availability Formula for Clustering)?


EJB programming & troubleshooting: Mastering EJB3 Chapter 19(Availability Formula for Clustering)?

  1. Hi, I am facing problem in understanding the formula mentioned in chapter 19 in Mastering EJB3 page 571 for "Calculating Availabilty of clustering"? probabilty of availability of servers= 1/m un availability of servers = (1-1/m)n where n = no of servers in cluster as power of factor (1-1/m). Kindly explain above formula and factor 1/m. regards Faisal
  2. Ok! Let me see how can I put it, suppose you have a dice, the probability of getting 2 is 1/6 and the probability of not getting 2 is 5/6 because the sum will have to be always 1. So if the probability of an applications server being available is 1/m then unavailability is 1-1/m.Now this is about single server, now let us have n servers and all are unavailable then total for the whole system will be (1-1/m)*(1-1/m)....n times.So maths says the unavailability will always decrease as you will increase n.True. I dont know If I have explained anything or confused you more but i tried. cheers,
  3. Hi Arijit I think faisal is trying to know the meaning of the factor m, i.e. is this the number of application servers or number of modules in the application. Further this will clear my understanding too in this regard.