Re: [ntp:questions] Pool server gone wild
On Sat, 21 Feb 2015 18:44:54 + (UTC), William Unruh un...@invalid.ca wrote: Why should it not continue to poll it? It should be pruned as a bad ticker by the ntpd algorihm, and thus not affect the clock discipline. But that offset might be just a temporary abberation and that source come back on sync in a few hours or days. Why throw it away. And as has been mentioned, apparently the pool servers are monitored and if a source is persistantly bad, it will be removed from the pool. Ie, what is the harm in continuing to poll it? To prune or not to prune, that is the question. If the design of the pool command is that ntpd should drop a server which is obviously wrong then it should drop it and the question is why didn't that happen in my case. It's possible that my understanding of the pool command is faulty and that ntpd behaved as designed. If that is so I should like to be told that I am mistaken. The design of the pool command is something you'll have to discuss with others. -- Roger ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Type 28 driver (gpsd, SHM) - understanding flag1
Le 21 févr. 2015 à 08:37, David Taylor david-tay...@blueyonder.co.uk.invalid a écrit : Folks, I'm looking at: http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver28.html and wanting to be sure that I understand flag1 correctly. The situation is starting a computer which has no real-time clock, and has been down for a day. This computer is in the middle of nowhere, and has a GPS and PPS as reference clocks, using the type 22 and type 28 drivers. By observation, the type 22 (PPS) driver won't kick in until the type 28 (SHM/gpsd) driver is valid, but also by observation with no flags set it seems that the type 28 driver never syncs at all, even though valid GPS data is present. My reading of that page is: - the default, flag1 = 0 or absent, and no time2 set, NTP will not kick in unless the local clock is within 4 hours of the GPS time. It seems that even with -g as an ntpd parameter, which /should/ allow a large initial offset NTP won't kick in. In the computer in question, the difference is likely to be in excess of 24 hours, so NTP will not attempt to correct the clock. This is not the desired behaviour! Is my understanding correct? Would the correct thing to do in such circumstances be to set flag1 = 1 so that the difference limit is ignored? My aged understanding concurs with yours. Set flag 1. Maybe not your desired behavior, but possibly that of the designer. I ask what may be an obvious question as I appear to have difficulty in reading the page. Perhaps old age, I hope nothing more! I suppose I had expect the -g to override other sanity checks. -- Thanks, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
David Taylor wrote: On 21/02/2015 07:04, William Unruh wrote: [] orphan mode is about a group of computers. Orphan Mode allows a group of ntpd processes to automonously select a leader in the event that all real time sources become unreachable (i.e. are inaccessible). chrony's is that you can enter the time by hand (Ie, by typing a current time and hitting enter) on a single machine. You are the remote clock. Now, how useful that is now adays is open to question, but in the past with telephone modems and flaky connections it was worth something. And if you are setting up something on the Hebrides or on a buoy in the Atlantic where no connection of anykind is possible, it could be useful. Ie, it IS different from orphan mode. Things chronyd can do that ntpd can?t: chronyd provides support for isolated networks whether the only method of time correction is manual entry (e.g. by the administrator looking at a clock). The claim is for networks, not single machines. When I was on dialup with Demon, I used chrony on the dialup pc and my network of several pcs, mostly with ntpd, synced to that. I'd have a problem looking up the logs that far back but I don't think drift from chrony offline was above a few ms. My pcs in the late 80s through early 90s seemed to have better system clocks than modern pcs and also had provision to use an external source as system clock. David ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
On Fri, 20 Feb 2015 19:19:43 +, Roger invalid@invalid.invalid wrote: Terje made the suggestion about too few servers. DNS returns 4 IP addresses at a time. By having four lines ntpd could have 12 different IP addresses returned if it used all four lines. Roger, repeat after me: 4 times 4 equals 16 ! How come nobody corrected that for me? -- Roger ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
On Fri, 20 Feb 2015 23:56:46 GMT, Brian Inglis brian.ing...@systematicsw.ab.ca wrote: Add iburst preempt to the ends of your pool server lines to improve startup and drop poorer sources. I'm only making one change at a time. That will come later. Using one pool line ntpd slowly increases the number of servers until it is happy but hasn't dropped any, not even an obviously rogue one. As DNS only returns 4 IP addresses that is the maximum it can start with and why it has to build up its numbers. Using multiple pool lines ntpd starts with more than it needs and after about 10 minutes starts dropping the ones it doesn't like. I restarted ntpd this morning. It solicited 13 servers all of which showed up in ntpq. After 10 minutes it started dropping servers. After 49 minutes it had dropped 7 servers. It would be useful if one of the remaining 6 goes rogue to see what, if anything, ntpd does. -- Roger ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Type 28 driver (gpsd, SHM) - understanding flag1
On 21/02/2015 08:33, Mike Cook wrote: [] My aged understanding concurs with yours. Set flag 1. Maybe not your desired behavior, but possibly that of the designer. [] Thanks, Mike. We are carrying out some tests, but it means leaving the computer down for at least several hours, and we've been trying about 24 hours down so far, so progress isn't rapid! If flag1 allows off-the-network operation after several days outage, that will be fine, but I will have to document it on my Web page. -- Cheers, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
On 21 Feb 2015 07:54:50 GMT, Rob nom...@example.com wrote: It looks like you have created your own problem. What problem are you talking about? -- Roger ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
On 21 Feb 2015 10:52:40 GMT, Rob nom...@example.com wrote: Roger invalid@invalid.invalid wrote: On 21 Feb 2015 07:54:50 GMT, Rob nom...@example.com wrote: It looks like you have created your own problem. What problem are you talking about? Your problem to get enough good servers. When did I say that? I observed ntpd continuing to poll a server which was off by 100s of milliseconds. Are you saying that ntpd didn't drop the server because of not enough good servers? A quick eyeball of the relevant peerstats shows that ntpd was using at least six good servers plus the one that went wild. Methinks you've come to an opinion based on too little information. -- Roger ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
Roger wrote: On 21 Feb 2015 10:52:40 GMT, Rob nom...@example.com wrote: Roger invalid@invalid.invalid wrote: On 21 Feb 2015 07:54:50 GMT, Rob nom...@example.com wrote: It looks like you have created your own problem. What problem are you talking about? Your problem to get enough good servers. When did I say that? I observed ntpd continuing to poll a server which was off by 100s of milliseconds. Are you saying that ntpd didn't drop the server because of not enough good servers? A quick eyeball of the relevant peerstats shows that ntpd was using at least six good servers plus the one that went wild. Methinks you've come to an opinion based on too little information. I haven't checked the source code for quite a while, but the limit used to be 10 servers, i.e. you needed more than 8 before it would try to prune the list and replace the worst to get back to 10. This limit is configurable, it might have been tweaked downwards. Terje -- - Terje.Mathisen at tmsw.no almost all programming can be viewed as an exercise in caching ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
Roger writes: Using one pool line ntpd slowly increases the number of servers until it is happy but hasn't dropped any, not even an obviously rogue one. As DNS only returns 4 IP addresses that is the maximum it can start with and why it has to build up its numbers. Yes, that is because before this we opened up too many. Dave Hart and I talked about this a while ago, and I've never had the time to go back and say We know how many more servers we'd like, let's have the pool directive open that many of them now. Using multiple pool lines ntpd starts with more than it needs and after about 10 minutes starts dropping the ones it doesn't like. I haven't see that case happen, but I haven't looked in a while either. I restarted ntpd this morning. It solicited 13 servers all of which showed up in ntpq. After 10 minutes it started dropping servers. After 49 minutes it had dropped 7 servers. It would be useful if one of the remaining 6 goes rogue to see what, if anything, ntpd does. It would also be swell to have a test case for this. H ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
Le 21 févr. 2015 à 10:00, Roger invalid@invalid.invalid a écrit : On Fri, 20 Feb 2015 19:19:43 +, Roger invalid@invalid.invalid wrote: Terje made the suggestion about too few servers. DNS returns 4 IP addresses at a time. By having four lines ntpd could have 12 different IP addresses returned if it used all four lines. Roger, repeat after me: 4 times 4 equals 16 ! How come nobody corrected that for me? My secondary school maths teacher used to make 'errors' like that to see if we were still awake. Mostly we weren’t either. -- Roger ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
William Unruh un...@invalid.ca wrote: On 2015-02-19, Rob nom...@example.com wrote: Miroslav Lichvar mlich...@redhat.com wrote: On Thu, Feb 19, 2015 at 12:48:46PM +, Rob wrote: I am still finding out what sensor is best to use, we do have a room temperature sensor that has .1C resolution and is readable via snmp, and there are the usual sensors for board- and inlet air temperature. (and of course CPU temperature) It does not matter if it is only a course indication, the room temperature varies over a -10 .. 50C range (don't ask...) and a 1C resolution is not bad relative to that. In my tests using a sensor with 1C resolution it was barely useful with NTP sources and 1024s polling interval. If the sensitivity is around 0.1 ppm per degree, 1C resolution means the compensation jumping the frequency in 0.1ppm steps. That's a lot, especially if you compare it to the tracking skew with a refclock. Ok but of course we are using PPS and a 16 second polling interval. (or maybe the PPS refclock polls even faster although it displays 4 as the poll interval indicator) The shm refclock will get one pulse per second, and then average the offsets over a 16 sec period after getting rid of the outliers. I am not using the SHM refclock in those systems. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
David Taylor writes: On 21/02/2015 07:04, William Unruh wrote: [] orphan mode is about a group of computers. Orphan Mode allows a group of ntpd processes to automonously select a leader in the event that all real time sources become unreachable (i.e. are inaccessible). chrony's is that you can enter the time by hand (Ie, by typing a current time and hitting enter) on a single machine. You are the remote clock. N ow, how useful that is now adays is open to question, but in the past with telephone modems and flaky connections it was worth something. And if you are setting up something on the Hebrides or on a buoy in the Atlantic where no connection of anykind is possible, it could be useful. Ie, it IS different from orphan mode. Things chronyd can do that ntpd can?t: chronyd provides support for isolated networks whether the only method of time correction is manual entry (e.g. by the administrator looking at a clock). The claim is for networks, not single machines. And how does ntpd not support this case? (David, I know this is not something you are claiming.) H ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
Roger invalid@invalid.invalid wrote: On 20 Feb 2015 19:29:44 GMT, Rob nom...@example.com wrote: Why not just: pool pool.ntp.org That should be enough. I did have just one line pool uk.pool.ntp.org but the rogue Did I write pool uk.pool.ntp.org? I don't think so... No, you didn't. Did I say that you did? It is what I had in my ntp.conf. That is why I suggested you change that. The region-specific codes are a leftover from the early days. Later, a geo-aware DNS was added and this is no longer required. server didn't get dropped even after 27 hours. I included the uk to try to make sure that the servers were as local as possible. Without that they could be anywhere in Europe. No, the pool.ntp.org name selects the closests servers. Close enough when you consider the pool good enough. Experience tells me that IP addresses are selected on a regional basis, not a country basis. Sometimes they are all in the UK, but not always. For example, earlier today one of the servers that was offered using pool.ntp.org was in Hungary. Putting the country code in makes it more likely that the IP addresses are local. But why do you worry? It does not matter if they are in the UK or Hungary. It would matter if they are in Brazil or in Australia, but that is not what is happening. It looks like you have created your own problem. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
William Unruh un...@invalid.ca wrote: On 2015-02-19, Rob nom...@example.com wrote: Miroslav Lichvar mlich...@redhat.com wrote: On Thu, Feb 19, 2015 at 10:05:45AM +, Rob wrote: We have systems in places that are not temperature controlled and then chrony is much better. I am looking for the best way to find the values to use in the tempcomp configuration directive. What resolution does the sensor have? Don't expect good results with 1C or 0.5C resolution that sensors on mainboards typically have. I am still finding out what sensor is best to use, we do have a room temperature sensor that has .1C resolution and is readable via snmp, and there are the usual sensors for board- and inlet air temperature. (and of course CPU temperature) It does not matter if it is only a course indication, the room temperature varies over a -10 .. 50C range (don't ask...) and a 1C resolution is not bad relative to that. It is of course the temperature of the crystal itself that is important. Ie, the room temp could be constant and the computer varies in its workload and thus its internal temperature. Unfortunately temp sensors on the crystal are rare in commodity computers. I am not looking for a precise crystal temperature but for a ballpark value that will compensate for the quick temperature swings that occur when this system (which is in an unheated glasshouse) quickly warms up when the sun rises, and cools down when the sun sets. In ntpd these events result in offset swings that are the derivative of the temperature. In chrony the swings are smaller, but it may be deceptive because I have not yet found a completely satisfactory way of gathering an average offset that is similar to the offset value in ntpq -c rv. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
Roger invalid@invalid.invalid wrote: On 21 Feb 2015 07:54:50 GMT, Rob nom...@example.com wrote: It looks like you have created your own problem. What problem are you talking about? Your problem to get enough good servers. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
On 2015-02-21 01:00, Rob wrote:
William Unruh un...@invalid.ca wrote:
On 2015-02-19, Rob nom...@example.com wrote:
Miroslav Lichvar mlich...@redhat.com wrote:
On Thu, Feb 19, 2015 at 10:05:45AM +, Rob wrote:
We have systems in places that are not temperature controlled and then
chrony is much better. I am looking for the best way to find the
values to use in the tempcomp configuration directive.
What resolution does the sensor have? Don't expect good results
with 1C or 0.5C resolution that sensors on mainboards typically have.
I am still finding out what sensor is best to use, we do have a room
temperature sensor that has .1C resolution and is readable via snmp,
and there are the usual sensors for board- and inlet air temperature.
(and of course CPU temperature)
It does not matter if it is only a course indication, the room temperature
varies over a -10 .. 50C range (don't ask...) and a 1C resolution is not
bad relative to that.
It is of course the temperature of the crystal itself that is important.
Ie, the room temp could be constant and the computer varies in its
workload and thus its internal temperature. Unfortunately temp sensors
on the crystal are rare in commodity computers.
I am not looking for a precise crystal temperature but for a ballpark
value that will compensate for the quick temperature swings that occur
when this system (which is in an unheated glasshouse) quickly warms up
when the sun rises, and cools down when the sun sets.
In ntpd these events result in offset swings that are the derivative
of the temperature. In chrony the swings are smaller, but it may be
deceptive because I have not yet found a completely satisfactory way
of gathering an average offset that is similar to the offset value
in ntpq -c rv.
Hi Rob,
If the systems can run x86/x64 Linux with Mono and WinForms or Windows
with .NET 2+ then OpenHardwareMonitor may be able to log the system
sensors.
For Linux see if lm_sensors/sensord/sensors/sensors-detect are available
on or for your system and look for data in:
/proc/acpi/thermal_zone/
/sys/bus/platform/devices/*temp*/
/sys/class/hwmon/hwmon[0-9]*/
/sys/class/thermal/{thermal_zone,cooling_device}[0-9]*/
Once you have the data, you may want to try weighted or windowed incremental
RMS values of temperature and frequency drift to see if they can be correlated.
--
Take care. Thanks, Brian Inglis
___
questions mailing list
questions@lists.ntp.org
http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Type 28 driver (gpsd, SHM) - understanding flag1
David Taylor writes: Thanks, Mike. We are carrying out some tests, but it means leaving the computer down for at least several hours, and we've been trying about 24 hours down so far, so progress isn't rapid! If flag1 allows off-the-network operation after several days outage, that will be fine, but I will have to document it on my Web page. Again, making corrections like this only on your web pages is counter-productive. It *hurts* NTP when incorrect information on the wiki or in the docs is not corrected. It *hurts* NTP when you take eyeballs away from our site, as we need all the help we can get to motivate folks to join or donate. -- Harlan Stenn st...@ntp.org http://networktimefoundation.org - be a member! ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Pool server gone wild
Roger invalid@invalid.invalid wrote: On 21 Feb 2015 10:52:40 GMT, Rob nom...@example.com wrote: Roger invalid@invalid.invalid wrote: On 21 Feb 2015 07:54:50 GMT, Rob nom...@example.com wrote: It looks like you have created your own problem. What problem are you talking about? Your problem to get enough good servers. When did I say that? I observed ntpd continuing to poll a server which was off by 100s of milliseconds. Are you saying that ntpd didn't drop the server because of not enough good servers? A quick eyeball of the relevant peerstats shows that ntpd was using at least six good servers plus the one that went wild. Methinks you've come to an opinion based on too little information. You started adding pool commands to add more and more servers, apparently because you believed there would be not enough to prune your bad server. I am amazed that you are using the NTP pool, while at the same time worrying about a bad server that is off by 100s of milliseconds, and then still not trust ntpd to reject it. The NTP pool is for people who want to sync there servers reasonably well, so the clock widget displays the right time when a human watches it. When you want guarantees, the NTP pool is not for you. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
On 2015-02-21, David Taylor david-tay...@blueyonder.co.uk.invalid wrote: On 21/02/2015 07:04, William Unruh wrote: [] orphan mode is about a group of computers. Orphan Mode allows a group of ntpd processes to automonously select a leader in the event that all real time sources become unreachable (i.e. are inaccessible). chrony's is that you can enter the time by hand (Ie, by typing a current time and hitting enter) on a single machine. You are the remote clock. Now, how useful that is now adays is open to question, but in the past with telephone modems and flaky connections it was worth something. And if you are setting up something on the Hebrides or on a buoy in the Atlantic where no connection of anykind is possible, it could be useful. Ie, it IS different from orphan mode. Things chronyd can do that ntpd can?t: chronyd provides support for isolated networks whether the only method of time correction is manual entry (e.g. by the administrator looking at a clock). The claim is for networks, not single machines. It will do that too. The crucial item there is the only method of time correction is manual entry which is different from ntpd and orphan mode. I have no idea why this conversation is continuing. The two are different. The two methods are trying to solve the same problem (timekeeping of isolated systems) but doing so in a different manner. If you like one better than the other, that is fine. But they are not the same. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
Brian Inglis brian.ing...@systematicsw.ab.ca wrote:
On 2015-02-21 01:00, Rob wrote:
William Unruh un...@invalid.ca wrote:
On 2015-02-19, Rob nom...@example.com wrote:
Miroslav Lichvar mlich...@redhat.com wrote:
On Thu, Feb 19, 2015 at 10:05:45AM +, Rob wrote:
We have systems in places that are not temperature controlled and then
chrony is much better. I am looking for the best way to find the
values to use in the tempcomp configuration directive.
What resolution does the sensor have? Don't expect good results
with 1C or 0.5C resolution that sensors on mainboards typically have.
I am still finding out what sensor is best to use, we do have a room
temperature sensor that has .1C resolution and is readable via snmp,
and there are the usual sensors for board- and inlet air temperature.
(and of course CPU temperature)
It does not matter if it is only a course indication, the room temperature
varies over a -10 .. 50C range (don't ask...) and a 1C resolution is not
bad relative to that.
It is of course the temperature of the crystal itself that is important.
Ie, the room temp could be constant and the computer varies in its
workload and thus its internal temperature. Unfortunately temp sensors
on the crystal are rare in commodity computers.
I am not looking for a precise crystal temperature but for a ballpark
value that will compensate for the quick temperature swings that occur
when this system (which is in an unheated glasshouse) quickly warms up
when the sun rises, and cools down when the sun sets.
In ntpd these events result in offset swings that are the derivative
of the temperature. In chrony the swings are smaller, but it may be
deceptive because I have not yet found a completely satisfactory way
of gathering an average offset that is similar to the offset value
in ntpq -c rv.
Hi Rob,
If the systems can run x86/x64 Linux with Mono and WinForms or Windows
with .NET 2+ then OpenHardwareMonitor may be able to log the system
sensors.
For Linux see if lm_sensors/sensord/sensors/sensors-detect are available
on or for your system and look for data in:
/proc/acpi/thermal_zone/
/sys/bus/platform/devices/*temp*/
/sys/class/hwmon/hwmon[0-9]*/
/sys/class/thermal/{thermal_zone,cooling_device}[0-9]*/
Once you have the data, you may want to try weighted or windowed incremental
RMS values of temperature and frequency drift to see if they can be
correlated.
I know how to access the sensors but I have not yet decided which sensor
is best to use, and how to calibrate the chrony configuration to it.
But even without the sensor input the offset is already much smaller than
with ntpd.
___
questions mailing list
questions@lists.ntp.org
http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
On 2015-02-21, Rob nom...@example.com wrote: William Unruh un...@invalid.ca wrote: On 2015-02-19, Rob nom...@example.com wrote: Miroslav Lichvar mlich...@redhat.com wrote: On Thu, Feb 19, 2015 at 10:05:45AM +, Rob wrote: We have systems in places that are not temperature controlled and then chrony is much better. I am looking for the best way to find the values to use in the tempcomp configuration directive. What resolution does the sensor have? Don't expect good results with 1C or 0.5C resolution that sensors on mainboards typically have. I am still finding out what sensor is best to use, we do have a room temperature sensor that has .1C resolution and is readable via snmp, and there are the usual sensors for board- and inlet air temperature. (and of course CPU temperature) It does not matter if it is only a course indication, the room temperature varies over a -10 .. 50C range (don't ask...) and a 1C resolution is not bad relative to that. It is of course the temperature of the crystal itself that is important. Ie, the room temp could be constant and the computer varies in its workload and thus its internal temperature. Unfortunately temp sensors on the crystal are rare in commodity computers. I am not looking for a precise crystal temperature but for a ballpark value that will compensate for the quick temperature swings that occur when this system (which is in an unheated glasshouse) quickly warms up when the sun rises, and cools down when the sun sets. It is the crystal temperature that determines the rate change. That crystal temp will be affected by the room temperature (with a lag since it it takes a while for the heat in the air to diffuse into the crystal--I have no idea how long that is, but is probably minutes rather than hours) how hard the machine is working (again the cpu heats up which eventually heats up the crystal) etc. One could probably use any of the temperature measurements that most motherboards have as proxies for the crystal temperature and get improved performance. Remember that the cpu temperature can vary by 20C which is probably more than the room does, and the motherboard forms a heat pipe from the cpu to the crystal. If you really want to study this, get a gps with a PPS and track the offset from the gps and one of those temperature measurements. You could switch off all clock discipline so that it cannot affect your measurements of rate as a function of temperature. Plot offset vs temperature. Look at the averaged slope of the curve to get a measure of how that temperature correlates with the rate. You could fit a curve (probably a quadratic in temperature would be fine.) Or run chrony or ntpd and plot the drift as a function of temperature with a low poll interval. chrony would probably be better in that it responds more quickly to changes in drift. (chrony has some tools for helping with this). Once you have measured this, you could use it in either the forks of ntpd which have temperature compensation, or with chrony. In ntpd these events result in offset swings that are the derivative of the temperature. In chrony the swings are smaller, but it may be deceptive because I have not yet found a completely satisfactory way of gathering an average offset that is similar to the offset value in ntpq -c rv. chrony's offset IS an average offset. It is fit to the past N measurements, where N varies depending on how good the linear fit is. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
On 2015-02-21, Rob nom...@example.com wrote: William Unruh un...@invalid.ca wrote: On 2015-02-19, Rob nom...@example.com wrote: Miroslav Lichvar mlich...@redhat.com wrote: On Thu, Feb 19, 2015 at 12:48:46PM +, Rob wrote: I am still finding out what sensor is best to use, we do have a room temperature sensor that has .1C resolution and is readable via snmp, and there are the usual sensors for board- and inlet air temperature. (and of course CPU temperature) It does not matter if it is only a course indication, the room temperature varies over a -10 .. 50C range (don't ask...) and a 1C resolution is not bad relative to that. In my tests using a sensor with 1C resolution it was barely useful with NTP sources and 1024s polling interval. If the sensitivity is around 0.1 ppm per degree, 1C resolution means the compensation jumping the frequency in 0.1ppm steps. That's a lot, especially if you compare it to the tracking skew with a refclock. Ok but of course we are using PPS and a 16 second polling interval. (or maybe the PPS refclock polls even faster although it displays 4 as the poll interval indicator) The shm refclock will get one pulse per second, and then average the offsets over a 16 sec period after getting rid of the outliers. I am not using the SHM refclock in those systems. What are you using? Are you on ntpd or chrony? As I recall ntpd in its pps refclock also collect say 16 outputs of PPS, finds the median, thros away the 40% greatest outliers and reports the resultant median to ntpd as the current offset. That is the same kind of filter chrony uses in its shm driver. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Type 28 driver (gpsd, SHM) - understanding flag1
On 21/02/2015 11:40, Harlan Stenn wrote: David Taylor writes: Thanks, Mike. We are carrying out some tests, but it means leaving the computer down for at least several hours, and we've been trying about 24 hours down so far, so progress isn't rapid! If flag1 allows off-the-network operation after several days outage, that will be fine, but I will have to document it on my Web page. Again, making corrections like this only on your web pages is counter-productive. It *hurts* NTP when incorrect information on the wiki or in the docs is not corrected. It *hurts* NTP when you take eyeballs away from our site, as we need all the help we can get to motivate folks to join or donate. I think there's a misunderstanding here! I am not saying that the information is incorrect, simply that I did not understand it. Until further tests are completed (by someone else), I will not know whether the extra flag is useful in our circumstances. Do you consider How to make an NTP server with a Raspberry Pi to be appropriate material for your site? It's the first I've heard of it, if so. These are the two pages which I hope to update: http://www.satsignal.eu/ntp/Raspberry-Pi-quickstart.html http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html I can add a pointer to your site if you would like to suggest a suitable starting page. -- Cheers, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
On Sat, Feb 21, 2015 at 1:57 AM, William Unruh un...@invalid.ca wrote: On 2015-02-21, Paul tik-...@bodosom.net wrote: On Fri, Feb 20, 2015 at 3:23 PM, William Unruh un...@invalid.ca wrote: ??? how do assume that the chrony docs do not tell the truth? ^ you Okay, I'll assume (or pretend) that you mean Why do I assume the Chrony documentation is in error and the answer is believing you. This is why I suggest you stop paraphrasing and stop asking for paraphrasing. Provide references to sources and stop doing original research. You said: Lichvar did some tests with PPS and found that chrony disciplined the clock much better than did ntpd (factors of over 10) and since NTPd can get to sub-microsecond your statement means Chrony is getting at least O(10) nanoseconds. The Chrony document says: With a good reference clock the accuracy can reach one microsecond. So one of you is wrong. Except it turns out you're both wrong. Miroslav Lichvar says If the clock is stable enough, they can perform similarly. so the Chrony doc understates the performance and you overstate it considering the current/recent state of the art. And now some original research: I switched my most challenging *client* (stratum 2 on a powerline network) from NTPd to Ntimed-client to Chrony. NTPd had excursions in O(10) to O(100) microseconds, Ntimed-client managed O(1) to O(10) microseconds and Chrony managed a reasonably consistent 1 millisecond offset. I used stock conf files except Ntimed-client doesn't use one. So points to Chrony for being more consistent. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Type 28 driver (gpsd, SHM) - understanding flag1
David Taylor writes: On 21/02/2015 11:40, Harlan Stenn wrote: David Taylor writes: Thanks, Mike. We are carrying out some tests, but it means leaving the computer down for at least several hours, and we've been trying about 24 hours down so far, so progress isn't rapid! If flag1 allows off-the-network operation after several days outage, that will be fine, but I will have to document it on my Web page. Again, making corrections like this only on your web pages is counter-productive. It *hurts* NTP when incorrect information on the wiki or in the docs is not corrected. It *hurts* NTP when you take eyeballs away from our site, as we need all the help we can get to motivate folks to join or donate. I think there's a misunderstanding here! I am not saying that the information is incorrect, simply that I did not understand it. Until further tests are completed (by someone else), I will not know whether the extra flag is useful in our circumstances. OK, then I'll rephrase to say that it benefits us all when the information on the NTP site is as good as possible, and it hurts the project when eyeballs are pulled away to other sites. Do you consider How to make an NTP server with a Raspberry Pi to be appropriate material for your site? It's the first I've heard of it, if so. These are the two pages which I hope to update: http://www.satsignal.eu/ntp/Raspberry-Pi-quickstart.html http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html Yes, that is appropriate material for the site. There are already pages for how to build for certain other platforms, and there is some fairly specific information about both hardware, BIOS, and software issues for some very specific platforms. Adding to that list on the support.ntp.org site *really* helps because it gets people to look there first, and when they see that the content has been added or improved by others they feel more comfortable adding or improving content themselves. Of course I do not actually *know* how other folks feel in this regard - it's my belief. I can add a pointer to your site if you would like to suggest a suitable starting page. The easy solution would be links to: - www.ntp.org The NTP Project Site - support.ntp.org The NTP Suppport Project - nwtime.org/why-join Become a supporting member of Network Time Foundation - nwtime.org/donate Donations to Network Time Foundation - www.nwtime.orgThe NTF main site We're happy to help in this area and recognize the efforts of folks and sites that help NTF be a success. -- Harlan Stenn st...@ntp.org http://networktimefoundation.org - be a member! ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
On 21/02/2015 17:52, William Unruh wrote: [] It will do that too. The crucial item there is the only method of time correction is manual entry which is different from ntpd and orphan mode. I have no idea why this conversation is continuing. The two are different. The two methods are trying to solve the same problem (timekeeping of isolated systems) but doing so in a different manner. If you like one better than the other, that is fine. But they are not the same. Bill, please enlighten me why I cannot, using NTP's orphan mode, set the time on one PC manually and have another PC sync to it? If you are saying that Chrony cannot work on isolated networks /without/ using manual time entry, I would consider that a significant disadvantage. I'm sure that isn't the case. I thought I might learn something about orphan mode from the discussion, as it's not something I have used or had the need for here. -- Cheers, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] chrony as a server
William Unruh un...@invalid.ca wrote: What are you using? Are you on ntpd or chrony? Please do not followup to my postings when you don't care to follow the thread! ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
