Matthew,
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. http://www.eecis.udel.edu/~mills/papers.html Rob 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 > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.