[time-nuts] Simple NTP server based on a Raspberry Pi
bell.peter at gmail.com
Mon Oct 29 23:48:48 EDT 2012
When I was playing around with the Raspberry PI, one of the things I
noticed that was the networking seemed to behave rather strangely at
times - not bad enough that you could really say it was broken, but
enough to reduce your level of confidence. Since I have previously
used that SMSC USB<->Ethernet bridge chip with no problems, I suspect
it's associated with the USB drivers on the PI.
On Tue, Oct 30, 2012 at 7:34 AM, Shaun Kelly <shaun at impsec.net> wrote:
> On 10/29/12 19:17 , Sarah White wrote:
>> On 10/29/2012 7:53 PM, Chris Albertson wrote:
>>> I'm curious what load average numbers do you get if you type "uptime"
>>> after running NTP for some hours.
>>> Basically, I'm thinking this method (raspi + refclock) is a good way to
>>> feed a handfull of public stratum 2 servers which by definition don't
>>> have their own local refclock.
>>> If you made your raspi stratum 1 server publicly available via
>>> pool.ntp.org it would almost certainly be overloaded.
> I have a Raspberry Pi in the pool now (ntp.impsec.net), though I've set
> bandwidth low (512k) so I am not seeing a great deal of load:
> root at ntp2:/home/pi# uptime
> 19:19:57 up 9 days, 21:54, 1 user, load average: 0.03, 0.08, 0.15
> top - 19:20:10 up 9 days, 21:54, 1 user, load average: 0.03, 0.08, 0.15
> Tasks: 55 total, 1 running, 54 sleeping, 0 stopped, 0 zombie
> %Cpu(s): 0.3 us, 0.2 sy, 0.0 ni, 93.9 id, 5.4 wa, 0.0 hi, 0.2 si, 0.0
> KiB Mem: 220652 total, 205332 used, 15320 free, 35256 buffers
> KiB Swap: 102396 total, 880 used, 101516 free, 145376 cached
> Watching with tcpdump I am seeing only a few packets per second average,
> withg some periods of burstiness where I see maybe 30 packets per second
> where it will maybe get up to 10-15% busy.
> [more snips]
>>> Let's assume a raspi can handle 200 packets per second without loosing
>>> performance too badly (limited by cpu load, etc.)
> I'd think that's probably close based on what I'm seeing, though again I'm
> just eyeballing tcpdump. Mind you, I'm not using the supported turbo modes
> so there might be some wiggle room with mild overclocking.
> (sig pending)
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