Re: Run NTP on zLinux or not?
I'm curious, have you looked at IBM's System z Academic Initiative program? https://www.ibm.com/developerworks/university/systemz/ It's been active for years, offers online training, classes at hundreds of colleges/universities, certifications, etc. It seems to get positive reviews. For z/Motivation it offers Enterprise Computing: Why you should teach it and your students should learn about it IBM continues to modernize and simplify the mainframe platform, while partnering with IBM customers, business partners and academia from around the world to build more of the skills that industry demands. There has never been a better time to teach your students about large systems. All of the top 25 world banks run their businesses on mainframes. 71% of global Fortune 500 companies are System z clients. 9 out of the top 10 global life/health insurance providers process their high-volume transactions on a mainframe. Ron Wells mailto:ron.we...@slfs.com>> said: no---and quality of students from schools are LOW... common sense gone .. and not enough / few schools training in MF for anything .. From: Jonathan Quay mailto:jonathan.q...@ihg.com>> Same way we got incented. Management makes a commitment to hire, train, and compensate zVM people. Do you see that happening in today's world of commodity hardware, open source software, and lowest common denominator application development? -- Gabriel Goldberg, Computers and Publishing, Inc. g...@gabegold.com 3401 Silver Maple Place, Falls Church, VA 22042 (703) 204-0433 LinkedIn: http://www.linkedin.com/in/gabegoldTwitter: GabeG0 -- 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/
Re: Run NTP on zLinux or not?
I turned 30 earlier this year, and I am a sysadmin since my twenties... I think the problem is that you can buy a computer to run Solaris, Windows, MacOS, MS-DOS, but you can't buy a computer to run zVM. I know some Linux admins as old as me, and they are very competent doing a reliable job, working for government, financial institutions, retail. The world thought that IBM was dying 20 years ago, and the mainframe was a dead platform. Almost every university and college stopped including mainframes on their courses, and the majority of people working with zVM today worked with mainframes 20 years ago. My graduation project was about virtualization on mainframes, and even my teachers does not knew anything about mainframes. My colleagues didn't either. And the learning curve for zVM is a strange one: the hardest, almost impossible part is getting started! "Step 1: buy a mainframe. Step 2: Install zVM. Step 3: have fun." I can install Vmware, Parallels, Xen, VirtualBox, and that product from Microsoft I forgot the name, all on my notebook, and install Linux, Windows, MacOS, Opensolaris, whatever. I can install a mainframe emulator too, but I cannot download zVM for it. I learned a lot when I was a zVM admin on my university, and some time we had 60 Linuxes, 3 zOS, 12 zVM and about 5000 users. I had to read a lot of redbooks, redpapers and ask Google a lot, but I was able to keep the system running nicely, and someday in 2007 we where running with memory overcommit of 6:1 on a z900 with a Shark F20 storage, and nobody complained. But I have some friends that would love to learn zVM, but they never got a chance because they cannot access a mainframe. If only IBM gave "educational licenses" to students, with a mainframe emulator, I think things would change a little... And zVM is as cool as any other hypervisor! Mauro http://mauro.limeiratem.com - registered Linux User: 294521 Scripture is both history, and a love letter from God. 2012/6/6 Michael MacIsaac : >> VM just isn't as fun as it once was. > Perhaps, but Linux more than makes up for that :)) > > "Mike MacIsaac" (845) 433-7061 > > -- > 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/
Re: Run NTP on zLinux or not?
> VM just isn't as fun as it once was. Perhaps, but Linux more than makes up for that :)) "Mike MacIsaac"(845) 433-7061 -- 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/
Re: Run NTP on zLinux or not?
I wouldn't mind seeing a thread about how we incent a new generation of z/VMers to start taking over the torch.. Over the next 10 years, our numbers are going to shrink drastically as many of us finally retire. My visions of proudly walking away someday knowing I've turned things over to competent hands are fading... Scott Rohling On Wed, Jun 6, 2012 at 7:55 AM, Dean, David (I/S) wrote: > Last post on my poll, I will not waste further cycles on a non-technical > issue here. I appreciate the people that emailed me offline. Rick, thanks > for the info. > > FINAL TOT BOARD FOR UNDER 35 YEARS OF AGE = 2 (nice try, bear, but no > cigar) > > I am not bashing zVM in any way, I am an evangelist and want only further > expansion, but as my teenage son constantly says to me, "I'm just sayin'..." > > > > > -Original Message- > From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of > r.stricklin > Sent: Monday, June 04, 2012 3:07 PM > To: LINUX-390@VM.MARIST.EDU > Subject: Re: Run NTP on zLinux or not? > > On Jun 4, 2012, at 11:23 AM, Dean, David (I/S) wrote: > > > Amen. We run it on 60 plus servers, started because of a tie in to > Active Directory on about 4 servers, but continued it on all servers solely > to work and play well with others. > > I had this requirement and found it sufficient to run 'ntpdate' from cron > once a day on those systems that needed it. > > > What would REALLY be interesting to know is how many of the daily > readers on this site are under 35 years old. Hope I am wrong...but > > FWIW I've been subscribed for about five years... but turned 35 last month. > > > ok > bear. > -- > 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/ > - > Please see the following link for the BlueCross BlueShield of Tennessee > E-mail disclaimer: http://www.bcbst.com/email_disclaimer.shtm > > -- > 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/
Re: Run NTP on zLinux or not?
I think there's also the factor that most are well into their 30's before they mature enough to understand that getting the job done reliably is more important in the long run than flash and sizzle. Ron Wells' post makes a good point, but the fact is that as it settles into its hipervisor roll, VM just isn't as fun as it once was. -- Mike Harding z/VM System Support mhard...@us.ibm.com mikehard...@mindless.com (925) 926-3179 (w) (925) 323-2070 (c) /sp Linux on 390 Port wrote on 06/06/2012 08:46:42 AM: > From: Scott Rohling > To: LINUX-390@vm.marist.edu > Date: 06/06/2012 09:38 AM > Subject: Re: Run NTP on zLinux or not? > Sent by: Linux on 390 Port > > I wouldn't mind seeing a thread about how we incent a new generation of > z/VMers to start taking over the torch.. Over the next 10 years, our > numbers are going to shrink drastically as many of us finally retire. My > visions of proudly walking away someday knowing I've turned things over to > competent hands are fading... > > Scott Rohling > > On Wed, Jun 6, 2012 at 7:55 AM, Dean, David (I/S) wrote: > > > Last post on my poll, I will not waste further cycles on a non-technical > > issue here. I appreciate the people that emailed me offline. Rick, thanks > > for the info. > > > > FINAL TOT BOARD FOR UNDER 35 YEARS OF AGE = 2 (nice try, bear, but no > > cigar) > > > > I am not bashing zVM in any way, I am an evangelist and want only further > > expansion, but as my teenage son constantly says to me, "I'm just sayin'..." -- 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/
Re: Run NTP on zLinux or not?
no---and quality of students from schools are LOW... common sense gone .. and not enough / few schools training in MF for anything .. From: Jonathan Quay To: LINUX-390@VM.MARIST.EDU Date: 06/06/2012 11:50 AM Subject:Re: Run NTP on zLinux or not? Sent by:Linux on 390 Port Same way we got incented. Management makes a commitment to hire, train, and compensate zVM people. Do you see that happening in today's world of commodity hardware, open source software, and lowest common denominator application development? -- 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/ -- Email Disclaimer This E-mail contains confidential information belonging to the sender, which may be legally privileged information. This information is intended only for the use of the individual or entity addressed above. If you are not the intended recipient, or an employee or agent responsible for delivering it to the intended recipient, you are hereby notified that any disclosure, copying, distribution, or the taking of any action in reliance on the contents of the E-mail or attached files is strictly prohibited. -- 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/
Re: Run NTP on zLinux or not?
Same way we got incented. Management makes a commitment to hire, train, and compensate zVM people. Do you see that happening in today's world of commodity hardware, open source software, and lowest common denominator application development? -- 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/
Re: Run NTP on zLinux or not?
Last post on my poll, I will not waste further cycles on a non-technical issue here. I appreciate the people that emailed me offline. Rick, thanks for the info. FINAL TOT BOARD FOR UNDER 35 YEARS OF AGE = 2 (nice try, bear, but no cigar) I am not bashing zVM in any way, I am an evangelist and want only further expansion, but as my teenage son constantly says to me, "I'm just sayin'..." -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of r.stricklin Sent: Monday, June 04, 2012 3:07 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Run NTP on zLinux or not? On Jun 4, 2012, at 11:23 AM, Dean, David (I/S) wrote: > Amen. We run it on 60 plus servers, started because of a tie in to Active > Directory on about 4 servers, but continued it on all servers solely to work > and play well with others. I had this requirement and found it sufficient to run 'ntpdate' from cron once a day on those systems that needed it. > What would REALLY be interesting to know is how many of the daily readers on > this site are under 35 years old. Hope I am wrong...but FWIW I've been subscribed for about five years... but turned 35 last month. ok bear. -- 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/ - Please see the following link for the BlueCross BlueShield of Tennessee E-mail disclaimer: http://www.bcbst.com/email_disclaimer.shtm -- 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/
Re: Run NTP on zLinux or not?
> On Tue, Jun 5, 2012 at 8:33 AM, Patrick Spinler > wrote: > > > I'd suspect that just running ntpd would be a preferably option here. > > Otherwise, you will get a cron awakened activity / network peak as > > dozens or hundreds of servers all wake up and try to sync their time. It would depend a lot on the size of the guests and how good your network time sources are. If the time sources are really good, probably wouldn't matter much (and you'd probably only run ntpdate once a week or so anyway; for most things, a few microseconds skew isn't a big deal for general use). There are also a number of scripts out there to randomize cron task execution around a certain time window to deal with the "everyone wakes at once" issue. > > ntpd really is a very low impact service to run, both in terms of > > network and server resources. Agreed. It's not worth arguing over unless you're really really resource-constrained. -- db -- 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/
Re: Run NTP on zLinux or not?
Thanks Sirs Richard, John, DavidB, Rob, DavidD, Bear, Thomas, Patrick and Madame Marcy - I appreciate your input very much! I believe it has helped decide in favor implementing ntpd on Linux guests in this particular instance. A special thanks to Rob for his presentation which helped myself and others understand the science behind it for the case of z/VM and it's pengins... Scott Rohling On Tue, Jun 5, 2012 at 8:33 AM, Patrick Spinler wrote: > I'd suspect that just running ntpd would be a preferably option here. > Otherwise, you will get a cron awakened activity / network peak as > dozens or hundreds of servers all wake up and try to sync their time. > > ntpd really is a very low impact service to run, both in terms of > network and server resources. > > -- Pat > > On 06/04/2012 06:36 PM, Thomas Kern wrote: > > When we had linux on Z, we ran the ntpdate program once per day (before > start of > > business). On our current ESX and Oracle Virtualization (xen), we need > to run it every hour. > > > > /Tom Kern > > > > On 6/4/2012 12:31, David Boyes wrote: > >> Running NTP everywhere wakes every guest up periodically, so you waste > a fair amount of cycles waking up to do nothing for most guests. > >> > >> The clocks in Linux guests do drift slightly (even if the HW is synced > to STP) -- it's order of tenths of microseconds, but it does lose a little > (barely measurable) bit. > >> > >> The things that really care about time (like any service using Kerberos > security, or other things that use time as a salt in some other process) > need NTP because they don't work without completely accurate time. > >> Everything else can get along fine with running ntpdate once a day. > > > > -- > > 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/ > -- 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/
Re: Run NTP on zLinux or not?
I'd suspect that just running ntpd would be a preferably option here. Otherwise, you will get a cron awakened activity / network peak as dozens or hundreds of servers all wake up and try to sync their time. ntpd really is a very low impact service to run, both in terms of network and server resources. -- Pat On 06/04/2012 06:36 PM, Thomas Kern wrote: > When we had linux on Z, we ran the ntpdate program once per day (before start > of > business). On our current ESX and Oracle Virtualization (xen), we need to run > it every hour. > > /Tom Kern > > On 6/4/2012 12:31, David Boyes wrote: >> Running NTP everywhere wakes every guest up periodically, so you waste a >> fair amount of cycles waking up to do nothing for most guests. >> >> The clocks in Linux guests do drift slightly (even if the HW is synced to >> STP) -- it's order of tenths of microseconds, but it does lose a little >> (barely measurable) bit. >> >> The things that really care about time (like any service using Kerberos >> security, or other things that use time as a salt in some other process) >> need NTP because they don't work without completely accurate time. >> Everything else can get along fine with running ntpdate once a day. > > -- > 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/
Re: Run NTP on zLinux or not?
When we had linux on Z, we ran the ntpdate program once per day (before start of business). On our current ESX and Oracle Virtualization (xen), we need to run it every hour. /Tom Kern On 6/4/2012 12:31, David Boyes wrote: > Running NTP everywhere wakes every guest up periodically, so you waste a fair > amount of cycles waking up to do nothing for most guests. > > The clocks in Linux guests do drift slightly (even if the HW is synced to > STP) -- it's order of tenths of microseconds, but it does lose a little > (barely measurable) bit. > > The things that really care about time (like any service using Kerberos > security, or other things that use time as a salt in some other process) need > NTP because they don't work without completely accurate time. > Everything else can get along fine with running ntpdate once a day. -- 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/
Re: Run NTP on zLinux or not?
On Jun 4, 2012, at 11:23 AM, Dean, David (I/S) wrote: > Amen. We run it on 60 plus servers, started because of a tie in to Active > Directory on about 4 servers, but continued it on all servers solely to work > and play well with others. I had this requirement and found it sufficient to run 'ntpdate' from cron once a day on those systems that needed it. > What would REALLY be interesting to know is how many of the daily readers on > this site are under 35 years old. Hope I am wrong...but FWIW I've been subscribed for about five years... but turned 35 last month. ok bear. -- 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/
Re: Run NTP on zLinux or not?
Excluding Marcy, of course. -Original Message- From: Dean, David (I/S) Sent: Monday, June 04, 2012 2:23 PM To: 'Linux on 390 Port' Subject: RE: Run NTP on zLinux or not? Amen. We run it on 60 plus servers, started because of a tie in to Active Directory on about 4 servers, but continued it on all servers solely to work and play well with others. I am 54 years old and come from a complete Window's background 1980-2003, not becoming a "convert" (partial) until 2004, which was not easy owing to the partisan nature of the young guys and the old guys. What would REALLY be interesting to know is how many of the daily readers on this site are under 35 years old. Hope I am wrong...but -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of David Boyes Sent: Monday, June 04, 2012 1:27 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Run NTP on zLinux or not? > Not running it is also one more > way to make your z type of Linux "different" from the x type of Linux. We > really don't need any more of those. > Marcy Yeah. What she said. -- 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/ - Please see the following link for the BlueCross BlueShield of Tennessee E-mail disclaimer: http://www.bcbst.com/email_disclaimer.shtm -- 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/
Re: Run NTP on zLinux or not?
Amen. We run it on 60 plus servers, started because of a tie in to Active Directory on about 4 servers, but continued it on all servers solely to work and play well with others. I am 54 years old and come from a complete Window's background 1980-2003, not becoming a "convert" (partial) until 2004, which was not easy owing to the partisan nature of the young guys and the old guys. What would REALLY be interesting to know is how many of the daily readers on this site are under 35 years old. Hope I am wrong...but -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of David Boyes Sent: Monday, June 04, 2012 1:27 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Run NTP on zLinux or not? > Not running it is also one more > way to make your z type of Linux "different" from the x type of Linux. We > really don't need any more of those. > Marcy Yeah. What she said. -- 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/ - Please see the following link for the BlueCross BlueShield of Tennessee E-mail disclaimer: http://www.bcbst.com/email_disclaimer.shtm -- 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/
Re: Run NTP on zLinux or not?
> Not running it is also one more > way to make your z type of Linux "different" from the x type of Linux. We > really don't need any more of those. > Marcy Yeah. What she said. -- 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/
Re: Run NTP on zLinux or not?
We run it. It is required by our Kerberos based authentication system and it is required by our security rules. It doesn't seem to take a lot of resources. Not running it is also one more way to make your z type of Linux "different" from the x type of Linux. We really don't need any more of those. We also run STP. The STP implementation on z/VM is for adjusting timestamps in I/O only. Yes, it helps when your LPAR is initially activated, but won't help you again on the z/VM side for any adjustments. Marcy -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Scott Rohling Sent: Monday, June 04, 2012 9:09 AM To: LINUX-390@VM.MARIST.EDU Subject: [LINUX-390] Run NTP on zLinux or not? 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/ -- 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/
Re: Run NTP on zLinux or not?
> > The things that really care about time (like any service using Kerberos > security, or other things that use time as a salt in some other process) need > NTP because they don't work without completely accurate time. > > Everything else can get along fine with running ntpdate once a day. > > IIRC Kerberos thinks about "not more than tens of seconds" where our > hardware clock drifts less than 2 seconds per month or so... Depends on your Kerberos config, and how paranoid your security admin is. Forestalls any argument about it if you have NTP enabled on systems that care about Kerberized services. OTOH, it's also an argument for having your Kerberos master services and NTP master services on the Linux on z system -- not hard to make the case for a stratum 3 time server from the STP clock source on the Z. Nice POC item, actually. -- 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/
Re: Run NTP on zLinux or not?
On Mon, Jun 4, 2012 at 6:31 PM, David Boyes wrote: > The things that really care about time (like any service using Kerberos > security, or other things that use time as a salt in some other process) need > NTP because they don't work without completely accurate time. > Everything else can get along fine with running ntpdate once a day. IIRC Kerberos thinks about "not more than tens of seconds" where our hardware clock drifts less than 2 seconds per month or so... Rob -- 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/
Re: Run NTP on zLinux or not?
On Mon, Jun 4, 2012 at 6:08 PM, Scott Rohling 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! I believe you should avoid running NTP on Linux when you can. The variation in latency a virtual machine gets on z/VM does not fit the model of network latency that NTP uses to get a reliable correction of the clock. My experience is that many configurations show larger swings with NTP than without. Your best bet is STP and ETR to have your hardware clock kept in synch with the world. If for some reason you can't have that, then run the ntp client at startup to once set the clock and keep following the (fairly stable) hardware clock. Most of what I claim in http://www.rvdheij.nl/Presentations/2005-L76.pdf still holds. Rob -- 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/
Re: Run NTP on zLinux or not?
Running NTP everywhere wakes every guest up periodically, so you waste a fair amount of cycles waking up to do nothing for most guests. The clocks in Linux guests do drift slightly (even if the HW is synced to STP) -- it's order of tenths of microseconds, but it does lose a little (barely measurable) bit. The things that really care about time (like any service using Kerberos security, or other things that use time as a salt in some other process) need NTP because they don't work without completely accurate time. Everything else can get along fine with running ntpdate once a day. -- 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/
Re: Run NTP on zLinux or not?
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 > 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/
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 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/
Run NTP on zLinux or not?
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/
