Re: [time-nuts] Beaglebone NTP server
On Thu, Dec 11, 2014 at 10:33 AM, Jim Lux jimlux@earthlink.net wrote:
Most national labs are more like time-nuts hobbyists for many of the same
reasons.
A big business (think cellphone provider) depreciates and amortizes their
gear, so they cycle through in 3-5 years, and build the update process
into the budget. They also buy in large quantities.
I was overly brief. A good example would Windows XP. Support from
Microsoft stopped in April or whenever. Except for the people with
contracts that said it didn't.
And some part of my brain knows that time distribution from NIST (I think
NIST not the Navy) is contracted out which presumably pushes all the
maintenance problems onto the contractor.
On Thu, Dec 11, 2014 at 10:27 AM, Dan Drown dan-timenuts@drown.org wrote:
Is this better or worse than other NTP server platforms? I haven't tested
them, so I have no idea.
Tharp says his appliance
"can sustain thousands of queries per second. Even under high throughput
timekeeping operations are never disrupted or perturbed."
But enough of that.
From the time-nut perspective what's the interest in high resolution NTP?
I mean beyond the "can I do this?" appeal.
Discussing the lifetime of NTP server hardware is all well and good but
given the thrust of this list, i.e. individual time-nuttery, I don't see it
as being too germane. Few of us have the same problems that Jim Lux has at
JPL.
I want to have a good time and frequency source in my little network that I
run. I can put an extra BBB or two aside to run NTP. Eventually I will want
to replace it but I bet that there will be an adequate SBC and free OS to
do that when need arises.
So, I am still looking for a straight-forward, "here is a really good way
to use a BBB coupled to a GPS 1pps to do NTP," treatise. Better still if
someone is using their LTE-lite to do it. It seems like a nice little
package for the amateur time-nut for everyday time and frequency keeping.
Oh, and if it has nixie tubes to display current time, umso besser! After
all, I still need to set my old-style watch and a few mechanical
chronographs I have kicking around.
--
Brian Lloyd
Lloyd Aviation
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
On 12/11/14, 7:35 AM, Paul wrote:
On Thu, Dec 11, 2014 at 9:59 AM, Jim Lux jimlux@earthlink.net wrote:
Linux isn't a whole lot better. If you have a system you cobbled together
in 2004
In the PPS via GPIO this is an issue and you don't have to go back 10
years. There's been a major change between (I think) 3.8 and later
kernels which makes some things much easier but breaks other things.
To be clear my comments aren't about
complex and subtle $10k lab instruments. They're specifically about 'my
two year old BBB doesn't work like my new one'. NTP servers are readily
done as a real appliance. Not a stripped down OS of choice box that is
hosting NTPD that someone calls an 'appliance'.
Maybe that's the key.. think of it as an appliance. If it stops working,
and it's not because of something simple (power cord), then you're
probably better off building a new one from scratch than trying to fix
the old one.
That is, the labor involved in "port to a new platform" might be
substantially less than "find old platform and install it in old box",
if only because things like tool chains tend to follow the latest hardware.
Even if you kept the tool chain for your old platform, running it on a
new computer might be problematic. (recognizing that there are people
out there running IBM 1401 emulators on System/360 emulators on... but
that takes time too)
Most folks don't try to repair their 20 year old toaster or refrigerator
or TV that has non-trivially failed.
I'm speaking as someone who just replaced a 17 year old refrigerator.
After 2 weeks of diagnosis and small scale fix attempts, the $2000 was
painful, but as it happens, the electricity cost of $200-300/yr is a lot
more than the $120/yr annualized cost of the refrigerator. The new
refrigerator has a measured power consumption <1/2 the old one, so if
it lasts 15 years (my observed typical refrigerator life expectancy) the
lower electrical costs will make up for the expense.
On Thu, Dec 11, 2014 at 10:03 AM, Paul tic-toc@bodosom.net wrote:
On Thu, Dec 11, 2014 at 10:27 AM, Dan Drown dan-timenuts@drown.org
wrote:
Is this better or worse than other NTP server platforms? I haven't
tested
them, so I have no idea.
Tharp says his appliance
"can sustain thousands of queries per second. Even under high throughput
timekeeping operations are never disrupted or perturbed."
But enough of that.
From the time-nut perspective what's the interest in high resolution NTP?
I mean beyond the "can I do this?" appeal.
We are all time nuts to one degree or another or we wouldn't be here. I
personally want all the clocks in my house, including all the computers (I
have about 10 running at any given moment here), to have time resolution
better than my ability to perceive errors. (To my eye that is about 100ms
for clocks with a sweep second hand.) and in the 1ms-or-better range for
the computers. I want to know that, when two things get time-stamped on
different machines, I can tell which happened first from the point of view
of a DBMS dealing with concurrency issues.
So a stratum 1 server in my house that is independent of my external
internet connectivity seems desirable.
Look, I used to leave WWV running all the time on a receiver. That
background DOOOO DOOOO DOOOO was very reassuring as I moved through the
house watching the sweep second hands ticking in time with WWV. Time to
move forward in true time-nut fashion.
--
Brian Lloyd
Lloyd Aviation
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
[]
So, I am still looking for a straight-forward, "here is a really good way
to use a BBB coupled to a GPS 1pps to do NTP," treatise. Better still if
someone is using their LTE-lite to do it. It seems like a nice little
package for the amateur time-nut for everyday time and frequency keeping.
[]
Brian Lloyd
---===
If it helps, Brian, my notes for doing the same thing with a Raspberry Pi
are here:
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html
Includes a wall-clock but no nixies:
http://www.satsignal.eu/raspberry-pi/DigitalClock.html
Cheers,
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Quoting Paul tic-toc@bodosom.net:
From the time-nut perspective what's the interest in high resolution NTP?
I mean beyond the "can I do this?" appeal.
From a practical standpoint, I don't personally have any application
that benefits from sub-1s accuracy. I'm just doing it for fun and
learning.
On 12/11/14, 8:11 AM, Brian Lloyd wrote:
Discussing the lifetime of NTP server hardware is all well and good but
given the thrust of this list, i.e. individual time-nuttery, I don't see it
as being too germane. Few of us have the same problems that Jim Lux has at
JPL.
Actually, I think my point was that the problems I face at JPL are
essentially identical to the problems we face at home. I'm not in the
time and frequency group (and I don't know that they actually are better
off.. although they do have rooms full of good clocks), so in our areas,
we tend to have little point solutions to problems.
It's not like there's a big time/frequency infrastructure with free
spigots from the maser in every lab. You have to pay for this stuff on
your project funds, and a lot of times, it seems easier to find a one
time expense (summer hire intern!) than sign up for a perpetual monthly
charge plus the infrastructure change cost to pull the fiber/coax.
We do have NTP, of course. But network drops are about $30-40/month, so
in a lab, you might decide, hey, I can buy a widget for a few hundred
dollars, and I'll have a better than NTP time source forever. And if
you've got a student hire, buying that $200 unit off eBay or Amazon and
taping a GPS antenna to the window starts to look pretty attractive.
There's probably more than a 100 (certainly dozens) of little GPS
antennas all over the lab connected to a bewildering variety of
time/frequency sources in labs. Sure, there's a goodly number of
TrueTime/Fluke/Pendulum/Symmetricom boxes of various vintages and
models, but there's also all manner of home-grown stuff.
Those student projects.. What a great way to get someone in for a few
months on a sort of trial basis. They get a really nice senior project
and you both get to find out if JPL is the kind of place they'd like to
work. I will confess that the only student intern who I had doing a
timing related project didn't really become imbued with the true
fascination for time and time transfer that I was hoping. On the other
hand, it is truly a niche.. people often don't appreciate how important
it is, and how widely used it is.)
I want to have a good time and frequency source in my little network that I
run. I can put an extra BBB or two aside to run NTP. Eventually I will want
to replace it but I bet that there will be an adequate SBC and free OS to
do that when need arises.
Which is exactly what we do at work.. Lots of old PCs doing something,
but there's that "what do we do when the PC fails" question. Just like
at home, you've got a limited budget and time available. Do you stock a
couple extra BBBs or RPis? That costs money, and you need to have a
place to store them where you'll be able to find them.
Or do you hope that when it fails 5 years hence, you'll have time and
budget to rebuild?
So, I am still looking for a straight-forward, "here is a really good way
to use a BBB coupled to a GPS 1pps to do NTP," treatise. Better still if
someone is using their LTE-lite to do it. It seems like a nice little
package for the amateur time-nut for everyday time and frequency keeping.
Essentially, you want the equivalent of a Microsemi
(Symmetricom/TrueTime) XL-GPS with the right options for, say, $500 or less.
I do too.
But I'm also not under any illusion that when my homegrown unit fails
that I'll be able to fix it, or rebuild it for the same price. It will
depend on someone having done the redesign using whatever is available
then, and published the cookbook.
Oh, and if it has nixie tubes to display current time, umso besser! After
all, I still need to set my old-style watch and a few mechanical
chronographs I have kicking around.
On Thu, Dec 11, 2014 at 10:46 AM, Jim Lux jimlux@earthlink.net wrote:
Actually, I think my point was that the problems I face at JPL are
essentially identical to the problems we face at home. I'm not in the time
and frequency group (and I don't know that they actually are better off..
although they do have rooms full of good clocks), so in our areas, we tend
to have little point solutions to problems.
It's not like there's a big time/frequency infrastructure with free
spigots from the maser in every lab. You have to pay for this stuff on
your project funds, and a lot of times, it seems easier to find a one time
expense (summer hire intern!) than sign up for a perpetual monthly charge
plus the infrastructure change cost to pull the fiber/coax.
We do have NTP, of course. But network drops are about $30-40/month, so in
a lab, you might decide, hey, I can buy a widget for a few hundred dollars,
and I'll have a better than NTP time source forever. And if you've got a
student hire, buying that $200 unit off eBay or Amazon and taping a GPS
antenna to the window starts to look pretty attractive.
There's probably more than a 100 (certainly dozens) of little GPS antennas
all over the lab connected to a bewildering variety of time/frequency
sources in labs. Sure, there's a goodly number of TrueTime/Fluke/Pendulum/Symmetricom
boxes of various vintages and models, but there's also all manner of
home-grown stuff.
Has anyone there noticed the amount of time and money spent recreating the
same thing over and over? Sure, individually it is cheap but when you do
the same thing hundreds of times, it is no longer a tiny amount. Clearly it
is a common needed service/device that your IT (or whatever) dept could
provide for nearly nothing. Sheesh.
Which is exactly what we do at work.. Lots of old PCs doing something, but
there's that "what do we do when the PC fails" question. Just like at
home, you've got a limited budget and time available. Do you stock a
couple extra BBBs or RPis? That costs money, and you need to have a place
to store them where you'll be able to find them.
Why not? The freakin' things are down to about $35 for an RPi and $55 for a
BBB. And the price for this is going to go down again. (Well, eventually
fabbing the board and soldering the nearly-free components is going to
define the lower bound in price but the performance can't help but
increase.)
Or do you hope that when it fails 5 years hence, you'll have time and
budget to rebuild?
And in 5 years there will be equivalent or better hardware at the same
price point. Stay in and eat beans for dinner one night to pay for your new
NTP server.
So, I am still looking for a straight-forward, "here is a really good way
to use a BBB coupled to a GPS 1pps to do NTP," treatise. Better still if
someone is using their LTE-lite to do it. It seems like a nice little
package for the amateur time-nut for everyday time and frequency keeping.
Essentially, you want the equivalent of a Microsemi (Symmetricom/TrueTime)
XL-GPS with the right options for, say, $500 or less.
Well, it is looking like I can do this very nicely for about $250 including
the BBB or RPi, LTE-Lite, and a 1U rack-box. Yes I have to build a buffer
for the 1pps and 10MHz output but that has been covered here very nicely.
I do too.
But I'm also not under any illusion that when my homegrown unit fails that
I'll be able to fix it, or rebuild it for the same price. It will depend
on someone having done the redesign using whatever is available then, and
published the cookbook.
I'm still thinking that the spare RPi or two tucked into the box with the
OS already loaded and configured will go a long way toward making sure I
can recover and keep going for many years. I have a BBB with Debian running
NTP that has been running for about 5 months now without a reboot as just a
local NTP stratum-3 server for my local machines. Works pretty well so I am
satisfied that it is stable to do the job. Once it is started I don't
expect to be doing a lot of OS upgrades. If it only runs NTP and all the
other services/daemons are turned off, it is going to be pretty difficult
to exploit. If it ain't broke, don't fix it.
--
Brian Lloyd
Lloyd Aviation
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
On Thu, Dec 11, 2014 at 11:11 AM, Brian Lloyd brian@lloyd.aero wrote:
So, I am still looking for a straight-forward, "here is a really good way
to use a BBB coupled to a GPS 1pps to do NTP," treatise
Fellow time-nut Dan Drown has done this although he uses Chrony rather than
NTPd. The idea is the same but you'd probably have to compile ntpd with
PPS support.