[ntp:questions] Re: 15-second difference in time

Heiko Gerstung heiko.gerstung_removeme_ at meinberg.de
Wed Aug 2 08:26:39 UTC 2006

Hi, Dave!

Dave schrieb:
> Hello,
>     I've got a FreeBSD box acting as an ntp server for my local lan. All 
> boxes connect up to it for synchronization of time. I run a network capable 
> backup program called bacula and today while running a backup between two 
> machines i got an error that the time between the two differed by 15 
> seconds. I realize this isn't a lot of time, but reading the ntp docs i was 
> under the impression that ntp would keep all boxes on my lan within 
> milliseconds accurate of each other. If this is so i'd appreciate any 
> suggestions as to what my issue might be.
> Thanks.
> Dave.

We once had a customer using our LANTIME time servers on his database 
backup servers. Each night the system clock of that server experienced 
30-second-jumps and it turned out that he is using IDE/ATAPI harddisks 
and DMA transfer (IIRC) and his Linux kernel was loosing timer ticks due 
to the heavy I/O caused by nightly update jobs.

Sounds a little bit like your problem, doesn't it? :-)

Best regards,

Meinberg radio clocks: 25 years of accurate time worldwide

MEINBERG Radio Clocks

Stand alone ntp time servers and radio clocks based on GPS, DCF77 and 
IRIG. Rackmount and desktop versions and PCI slot cards.

More information about the questions mailing list