Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

Does anybody know if Ubuntu's NTP servers are redundant? If I dig them, I get:

;; ANSWER SECTION:
ntp.ubuntu.com.     280 IN  A   91.189.94.4

vs. when I dig pool.ntp.org:

;; ANSWER SECTION:
pool.ntp.org.       350 IN  A   173.244.211.10
pool.ntp.org.       350 IN  A   173.255.193.172
pool.ntp.org.       350 IN  A   209.114.111.1

Would this indicate that ntp.org might be more reliable?

share|improve this question
add comment

2 Answers

up vote 5 down vote accepted

The results you get from pool.ntp.org is a random selection from 3000 available servers in the network. The pool is constantly monitored, and badly performing systems are removed from the pool when they stop providing reliable time.

Ideally, you would want to use the pool servers from your region, which you can find by drilling down to find the closest selection from from the web site.

I am not sure how Ubuntu handles their NTP server internally, and short of asking them, there is no way to be certain. As a general rule though, you should be using NTP servers that you know to be reliable and are close to you.

In any case, you should always have a couple NTP servers defined, so you can just let the NTP protocol pick the best source of time.

share|improve this answer
1  
The NTP pool project does geo-DNS, so simply picking pool.ntp.org or 0.pool.ntp.org, 1.pool.ntp.org, etc. should give you servers in your own country, or failing that, in a nearby country. Use of the "0.", "1.", "2." prefixes produces a disjoint set of servers, so you can be guaranteed you will have multiple upstream sources. –  rmalayter Jun 15 '12 at 14:16
add comment

If you want redundancy in ntpd, use multiple servers. When using a round-robin DNS record (such as the one for pool.ntp.org), only one IPv4 or IPv6 server is selected for a 'server pool.ntp.org' line. Repeating the line 3 times will select 3 different servers from the pool.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.