>> So, I ask, is I/O tuning still possible, or even necessary? >> .. >> I believe you can run them quite high, well over 50%. >> Since (the simple equation), the odds of all four being busy is: >> >> 5 ** 4 = .125 >> >> Or 12.5% of the time there would be no channel busy. >> Of course, you have to calculate the 'Relative Path Busy', since your own >I/O doesn't count. >> But, I did say 'simple'. >> > >Beware: .5 **4 = 0.0625, 6% of the time no path is busy. >It also means that (1-.5) ** 4 = 0.0625 6% if the time all paths are busy >and you will encounter delays and this sounds a little high to me. > >.5 ** 6 = 1.5% all paths busy >.6 ** 8 = 1.6% all paths busy >
I/O tuning is still alive, especially in DASD replication projects. However, it takes time and practice to build I/O tuning skills. The formula (Utilization ** 4) just doesn't work. It's not even close. The math is much more complex, and we can't simplify some things. It could make a huge difference. To make the story short, for 4 paths at 50%, "the probability of all busy" is approx 17%. As I said, it takes time. But the effort can certainly pay off. Regards, Robert Hamilton ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
