Recommended Number of NTP Servers

[Richard Laager]

The default for maxclock is 10. This includes the "pool" entries, of
which the stock Debian configuration has four:
pool 0.debian.pool.ntp.org iburst
pool 1.debian.pool.ntp.org iburst
pool 2.debian.pool.ntp.org iburst
pool 3.debian.pool.ntp.org iburst

As a result, the default is to use 6 pool servers.

http://support.ntp.org/bin/view/Support/SelectingOffsiteNTPServers says
"the general rule is for 2n+1 to protect against 'n' falsetickers". (It
goes on to discuss the exception for n=1, which is not relevant here.)

If that's true, then it seems like odd numbers of servers are better,
all things being equal. From there, it seems like I should set maxclock
to either 11 (so 11-4 = 7 servers) or 9 (so 9-4 = 5 servers). Any flaws
in this logic?

Any thoughts on whether 7 servers or 5 servers is better? The same page
says, "Conventional wisdom is that using at least five upstream time
servers would probably be a good idea, and you may want more." The
conservative choice is 7, but is that likely to make a meaningful
difference compared to 5?

-- 
Richard