I have a vague memory that Linux on z does not use the "timer tick" that some other platforms use. That it uses the z's hardware clock for timing. I think it was the "tickless kernel"? But I don't have a Linux on z system here anymore. Even without STP, the hardware clock is very accurate. I don't think that we've reset it since we installed the hardware - about 6 years ago.
-- John McKown Systems Engineer IV IT Administrative Services Group HealthMarkets® 9151 Boulevard 26 . N. Richland Hills . TX 76010 (817) 255-3225 phone . john.mck...@healthmarkets.com . www.HealthMarkets.com Confidentiality Notice: This e-mail message may contain confidential or proprietary information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. HealthMarkets® is the brand name for products underwritten and issued by the insurance subsidiaries of HealthMarkets, Inc. -The Chesapeake Life Insurance Company®, Mid-West National Life Insurance Company of TennesseeSM and The MEGA Life and Health Insurance Company.SM > -----Original Message----- > From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On > Behalf Of Richard Troth > Sent: Monday, June 04, 2012 11:22 AM > To: LINUX-390@VM.MARIST.EDU > Subject: Re: Run NTP on zLinux or not? > > Recommendation leans toward "no", but is not firm. > > Back before we had STP, I used to say "no", then changed my story to > "yes, run it". Lately not so sure. > > 6 or 7 or more years ago, the point was ... dozens or hundreds of > Linux guests ... do you want them all running NTP? At first, "we" > said no way! But it turned out that NTP was one of the better behaved > services on Linux. It starts, samples time, sleeps for a really long > time, wakes and makes comparisons, maybe adjusts, sleeps more. It was > the first thing we turned off, but turned out to be the LAST thing we > NEEDED to turn off. > > That was before STP. STP changes things. Lately, I'm just not sure, > and I don't have measurement to know ... yet. > > I also hear from at least one person who has studied it that he STILL > does not recommend NTP on the guests. > > In any case, the mainframe clock has always been way more stable than > other HW platforms. If your build of NTP includes the stand-alone > 'ntpdate' program, you could run that at IPL time and then > OCCASIONALLY. > > -- R; > Rick Troth > Velocity Software > http://www.velocitysoftware.com/ > > > On Mon, Jun 4, 2012 at 12:08 PM, Scott Rohling > <scott.rohl...@gmail.com> wrote: > > Was having a conversation today about running Linux on > System z and whether > > it needed to run an NTP client -- the statement being STP > is used to keep > > the mainframe time in synch, so why run NTP on a Linux > guest - the system > > time is correct. My understanding is that Linux maintains > it's own clock > > so even if z/VM fully supported STP, it doesn't mean the > guests would > > necessarily benefit. I haven't done a lot of research into time > > synchronization, so I thought I'd ask what others here do > and why. Any > > input would be appreciated! > > > > Scott Rohling > > > > > ---------------------------------------------------------------------- > > For LINUX-390 subscribe / signoff / archive access instructions, > > send email to lists...@vm.marist.edu with the message: INFO > LINUX-390 or visit > > http://www.marist.edu/htbin/wlvindex?LINUX-390 > > > ---------------------------------------------------------------------- > > For more information on Linux on System z, visit > > http://wiki.linuxvm.org/ > > > > -- > -- R; > Rick Troth > Velocity Software > http://www.velocitysoftware.com/ > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to lists...@vm.marist.edu with the message: INFO > LINUX-390 or visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > ---------------------------------------------------------------------- > For more information on Linux on System z, visit > http://wiki.linuxvm.org/ > > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
