[time-nuts] Best OS for small time server

Robert Vassar rvassar at rob-vassar.com
Thu Feb 21 18:29:23 EST 2008


I live in Texas, so I have something more than a passing familiarity  
with oppressive heat.  In essence, every watt imported into my den  
has to be forcibly removed 9 months of the year, if not more.  I  
maintain a low stratum NTP server at home, sadly not stratum 1 (yet!)  
on a small machine that runs 24x7.  In addition to NTP duty, it hosts  
some network filesystems, DHCP, periodic batch jobs via cron (rsync,  
etc...), and provides a ssh landing pad.  I used to run this on an  
old SPARC IPX, later a Pentium-1, followed by a Pentium Pro PC,  
etc...  The heat & noise started getting to me.  I picked up a  
Linksys NSLU2 network storage widget and hacked into it.  It runs a  
minimal Linux system on a very low power ARM processor, and uses USB  
attach disk storage.

I successfully ran these network services sans network filesystems on  
a 1Gb USB memory stick for about 8 months.  It was completely silent,  
and the total power draw was roughly 5 watts.  The problem I ran into  
is that  Linux implements a POSIX compliant filesystem.  Even taking  
steps to eliminate swap, the never ending filesystem metadata updates  
burned up my little flash drive in less than a year.  BSD will not  
escape this problem.  It will be true on any system that records file  
access/modify timestamps.  There might be a way to turn them off, or  
you might be able to mount certain partitions read-only.

I've since gone back to a full size (~90mm) USB attach disk.  It  
takes a bit more power, and makes a bit more noise, but it gets the  
job done, and should have a 5 year life span.  I don't think a NSLU2  
could be adapted for stratum 1 NTP use without some serious hacking,  
as a serial port would be a USB dongle.  But I thought you'd fine the  
flash disk results interesting.

Beyond this, Dave Mills, the author of NTP has a great paper on high  
resolution timekeeping in Unix kernels.  It's a bit dated, circa  
1994, but it might be worth a read.  I'm not sure if Linux follows  
his guidelines or not.  I believe Solaris and several of the BSD's do.



On Feb 21, 2008, at 4:36 PM, Matthew Smith wrote:

> Quoth Jason Rabel at 2008-02-21 14:14...
> ...
>> FreeBSD will support a PPS signal natively. If you have a hard  
>> drive you
>> could just run a plain install, if you want to run off a  
>> CompactFlash module
>> then I would suggest building a NanoBSD image. It took me a few  
>> tries to get
>> it right but I'm very happy with the performance.
> I was going to use an old laptop disc for this as I have absolutely no
> experience with 'small' Un*x implementations - like what happens to
> /swap, etc.  However, I would prefer a system that uses as little  
> power
> as possible and has no moving parts, so should probably investigate  
> the
> CompactFlash option - I'll Google for NanoBSD.
> Just had a quick look on eBay - seems like I can get a CF to 44 pin
> laptop IDE adapter for $AUD 12 delivered and a 1Gb CF card for $AUD 30
> delivered (I'm assuming that 1Gb should be more than adequate for a
> system like this).  So, not expensive, probably worth a go.
>> ntpns currently only supports the Oncore & dcf77 receivers, so its  
>> not for
>> everyone. I have it running on my net4501 w/Oncore UT+ and it has  
>> been
>> happily humming away.
> I've got a couple of Oncores in my desk somewhere, but they are  
> just the
> GT model.  I think that the Trimble ACE II has better PPS accuracy  
> than
> these, although I'd have to check.
>> Besides a "time server" what other features are you looking for?
> If you mean what else do I want this box to do, haven't really  
> decided.
>  As I have the components kicking around, I thought that it would be
> nice to run my own Stratum I time server, rather than having to  
> rely on
> the local Stratum II pool (may keep this for sanity checking though).
> As our power is not all that reliable here (on the end of a LONG  
> Single
> Wire, Earth Return 19kV line), I wanted something that could run off a
> trickle-charged sealed lead acid battery, rather than further  
> burdening
> my main UPS - which only runs for an hour anyway.
> I have been giving some thought to having an external USB hard disc on
> the thing for my server backups.  Currently, I have a Sun Blade 100
> doing this job - uses a bit more power than is really necessary. (And
> adds to the heat problem in my office in the cruel South Australian
> Summer.  But keeps it nice and warm in Winter.)
> I've thought of building some radio-controlled (434MHz Aussie ISM  
> band)
> slave clocks, but don't know if I'll use this as the master, or use a
> separate receiver.  More on that another time - I have some ideas for
> some rather 'different' clocks that I'd like to build.
> Cheers
> M
> -- 
> Matthew Smith
> Smiffytech - Technology Consulting & Web Application Development
> Business: http://www.smiffytech.com/
> Personal: http://www.smiffysplace.com/
> LinkedIn: http://www.linkedin.com/in/smiffy
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