[time-nuts] Simple NTP server based on a Raspberry Pi

Joseph Gray jgray at zianet.com
Tue Oct 30 00:00:28 EDT 2012


I have read that there were a number of people having various USB
problems. Some related to network, audio, etc. I understand that there
is work being done on the USB software. I don't know if the latest
version of Raspbian has fixed things or not. I'll be using a USB audio
dongle when my R-Pi arrives, so I guess I'll see...

Joe Gray
W5JG

On Mon, Oct 29, 2012 at 9:48 PM, Peter Bell <bell.peter at gmail.com> wrote:
> 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.
>
> Regards,
>
> Pete
>
>
> 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.
>>
>> [snips]
>>
>>>> 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
>> st
>> 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.
>>
>>
>> -Shaun
>> (sig pending)
>>
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