[rrd-users] recover from logged incorrect time

Rick Jones rick.jones2 at hp.com
Sat Feb 25 03:30:16 CET 2012

On 02/24/2012 02:28 PM, Steve Shipway wrote:
> We run ntp on our RRD/MRTG servers here, since time sync is so
> important, and I've never had this sort of issue.
> Are you sure that you're not getting a time synch issue with NTP
> rather than with RRDTool?  I don't know where you're ntpsynching
> from, or your ntpd params - maybe make sure that ntpd is set so it
> will not change the clock if is seems to be more than 1min out of
> synch (which would indicate an NTP issue).  A 1-hour error seems as
> if some server is confusing daylight savings time with the real
> time... if your servers are simply using ntpd to come to a consensus
> on time (via broadcast) rather than all synching from a single
> specified trusted source, a misconfigured server pushing out
> incorrect times somewhere on your network *might* do this?

That seems like an excellent opportunity to recount how NTP 
configuration best practice is to have at least four NTP servers 
configured - to allow for one to go away and still have three so the bad 
clock heuristics can still do their thing.  And that NTP does everything 
in UTC and cares not for timezones.

rick jones

> Steve
> Steve Shipway
> University of Auckland ITS
> UNIX Systems Design Lead
> s.shipway at auckland.ac.nz
> Ph: +64 9 373 7599 ext 86487
> ________________________________________
> From: rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch [rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch] on behalf of Otheus [otheus+rrd at gmail.com]
> Sent: Saturday, 25 February 2012 12:22 a.m.
> To: rrd-users at lists.oetiker.ch
> Subject: Re: [rrd-users] recover from logged incorrect time
> I have a related problem.
> On our server we're running RRDtool 1.4.4
> Remote monitoring servers connect to the RRDtool via TCP socket; rrdtool is
> configured on the server to run under xinetd in 'remote command' mode.
> Everything works fine most of the time.
> Once every few days, one or more servers will show that the last-update time
> is maybe one hour in the future. I fixed this once using the
> dump-edit-restore method. But that's not a solution for the long-run.
> The "correct" RRD databases show a timestamp which matches the wall-clock
> time according to perl's localtime() function. The incorrect one(s) will
> show a timestamp of about +3600 seconds.
> Is there a known problem with rrdtool in command mode that would lead to
> such clock skews? Could it be that ntp running on both hosts would interfere
> with rrdtool?
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