Ted, The rule of thumb I've heard is that you shouldn't run "channel busy + director port busy" over 50%.
In the real world, we've run them up 80% + 95%, respectively, before we saw degradation. After that point, it became an exponential curve to major delay (i.e. at 85% + 99% I/O bound batch that usually took 30 mins went to run times in the 4-6 hour range). I'd say if you can go to 8 channels in width, without incurring an unacceptable cost, go for it. It's better redundancy, resiliency, and the need for more data faster only increases over time so extra width is generally a good thing. Regards, Gary Diehl -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] Behalf Of Ted MacNEIL Sent: Sunday, June 12, 2005 7:00 PM To: [email protected] Subject: Re: Disk I/O tuning still possible? ... So, I ask, is I/O tuning still possible, or even necessary? ... I've got a related question. Our service provider is attempting to get us more channels into our single DASD controller. We have four. We have no Channel Busy Delay. We have more than adequate response time. They have supplied no evidence, as yet. My question is: What is considered “too busy” these days for channels? ---------------------------------------------------------------------- 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
