Hello all. I'd appreciate some help. I'm the defacto admin for a small research cluster in an academic institution. All hosts are running GNU/Linux under a 2.6.22-family kernel. The ntp version in use is 4.2.4 p4. My campus runs two ntp servers. My cluster's headnode uses the two campus ntp servers as its sources. Internal cluster nodes then use the cluster headnode as their (only) ntp time source. The internal cluster nodes have no route to the internet, only the headnode does.
I'm seeing a problem wherein internal cluster nodes develop significant clock skew over time. By "significant" I mean up to 700 seconds over two weeks of uptime. I am checking this using "ntpq -p" and looking at the offset field. The only thing I can think of is that some of the machines, including the headnode, are configured to use the Linux "ondemand" CPU frequency governor. These processors are older AMD Opteron 246/248 chips capable of dynamic frequency management. However, I also have nodes with older AMD Athlon processors that do not employ dynamic frequency management which also exhibit this phenomenon. Additionally, on the headnode I am seeing in the ntpd syslog output messages like: ntpd[5642]: frequency error 509 PPM exceeds tolerance 500 PPM But there are no such log entries on any of the internal nodes. Is there any issue with dynamic processor frequency control negatively affecting ntp? If this is not it, I can give the basic contents of my ntp.conf files. None of these machines are running onboard firewalls, and ntpd is being started through the init system. --- On the head node: Two sets of server directives in the form: server a.b.c.d iburst restrict a.b.c.d nomodify notrap nopeer noquery where a.b.c.d is one of the campus ntp servers' IP addresses. Thereafter there is: restrict default ignore restrict 127.0.0.1 restrict h.i.j.k mask l.m.n.o nomodify nopeer notrap where h.i.j.k and l.m.n.o are correctly defined to allow all the internal cluster hosts to query this machine followed by: restrict h.i.j.p mask 255.255.255.255 where p is the head node's internal cluster IP address. --- On the internal cluster nodes (all use the identical file): server h.i.j.p iburst where h.i.j.p is the headnode's IP address followed by: restrict default ignore restrict 127.0.0.1 restrict h.i.j.p mask 255.255.255.255 nopeer --- Thanks for any help. -- [EMAIL PROTECTED] -- http://www.fastmail.fm - The professional email service _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
