Scott > Using Jumbo Frames usually increases throughput by increasing link utilization.
I must be missing something here. If by improving the "efficiency" as defined in http://en.wikipedia.org/wiki/Ethernet_frame you get more throughput, why is that a bad thing? It might even solve the *problem* by addressing the *issue* of efficiency. It can always save an "IIRC" if you turn to the manual: Open Systems Adapter-Express Customer's Guide and Reference <quote> The OSA-Express Gigabit Ethernet feature: - ... - Provides 1000 Mbps/full duplex operation via point-to-point link - ... </quote> Chris Mason On Mon, 18 Apr 2011 15:12:54 -0400, Scott Rowe <[email protected]> wrote: >While switching to Jumbo Frames may be beneficial (assuming the current MTU >is set to 1500), it is not likely to solve the issue. Using Jumbo Frames >usually increases throughput by increasing link utilization. I kinda think >they are already using Jumbo Frames if they are getting 100MB+/s. One place >to check for this is the output from NETSTAT DEV for the OSA in question: >field ActMtu. > >As far as speed/duplex settings go, they are definitively set at 1Gb, or >they would not be getting throughput numbers that high, and IIRC, Gigabit is >ALWAYS full duplex. > >On Mon, Apr 18, 2011 at 1:55 PM, Blaicher, Chris <[email protected]>wrote: > >> I have never done ANY work with an OSA card, so my comment may be way >> off-track. >> >> Changing the size of the packet (if that is even possible in an OSA card), >> may buy you some reduction in the ratio of overhead bytes to data bytes. A >> friend was working on a problem with a saturated gigabit LAN and changed the >> packet size from the default to maximum and saw a huge gain. >> >> >> Christopher Y. Blaicher >> Senior Software Developer >> Austin Development Lab >> >> phone: 512.340.6154 >> mobile: 512.627.3803 >> fax: 512.340.6647 >> >> 10431 Morado Circle >> Austin, TX 78759 >> >> >> >> -----Original Message----- >> From: IBM Mainframe Discussion List [mailto:[email protected]] On >> Behalf Of Hal Merritt >> Sent: Monday, April 18, 2011 12:03 PM >> To: [email protected] >> Subject: Re: When is an OSA card too busy? >> >> Yes, but why? >> >> For example, we just recently had an issue where some piece of gear was >> configured as auto negotiate. After a lot of work, it was determined that >> the Cisco routers we were using don't do auto negotiate well and had somehow >> gotten into the wrong duplex state. >> >> We turned off auto and set speed and duplicity to fixed values. Made a huge >> difference. Huge. >> >> I'm thinking that networks bytes are far greater than payload bytes due to >> retries, etc. >> >> >> >> -----Original Message----- >> From: IBM Mainframe Discussion List [mailto:[email protected]] On >> Behalf Of Scott Rowe >> Sent: Monday, April 18, 2011 10:41 AM >> To: [email protected] >> Subject: Re: When is an OSA card too busy? >> >> So, this is a Gigabit OSA? If so, 100MB is close enough to theoretical >> maximum data rate that it's pretty safe to say it's maxed out. >> >> On Mon, Apr 18, 2011 at 11:30 AM, Horne, Jim - James S < >> [email protected]> wrote: >> >> > Yes, we've checked that and it's okay. >> > >> > Jim Horne >> > >> > -----Original Message----- >> > From: IBM Mainframe Discussion List [mailto:[email protected]] On >> > Behalf Of Scott Rowe >> > Sent: Monday, April 18, 2011 11:22 AM >> > To: [email protected] >> > Subject: Re: When is an OSA card too busy? >> > >> > Also, have you checked that the OSA is connected at the proper speed and >> > duplex? This can be done through the HMC. ---------------------------------------------------------------------- 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
