As far as I remember, you have to start digging into 'Eigen numbers' or something like that
-----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Vernooy, C.P. - SPLXM Sent: 14 June 2005 08:05 To: [email protected] Subject: Re: Disk I/O tuning still possible? "Robert Hamilton" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>... > >> 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%. > Could you elaborate this? I am not graduated in statistics, but I thought I knew something about it. Kees. ********************************************************************** For information, services and offers, please visit our web site: http://www.klm.com. This e-mail and any attachment may contain confidential and privileged material intended for the addressee only. If you are not the addressee, you are notified that no part of the e-mail or any attachment may be disclosed, copied or distributed, and that any other action related to this e-mail or attachment is strictly prohibited, and may be unlawful. If you have received this e-mail by error, please notify the sender immediately by return e-mail, and delete this message. Koninklijke Luchtvaart Maatschappij NV (KLM), its subsidiaries and/or its employees shall not be liable for the incorrect or incomplete transmission of this e-mail or any attachments, nor responsible for any delay in receipt. ********************************************************************** ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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
