Enhanced AutoFS Administrator's Guide

Configuring and Administering AutoFS
Configuring Multiple Servers for an AutoFS Directory
Chapter 3 47
The server chosen for the mount is the one with the strongest preference
based on a sorting order. The sorting order used gives strongest
preference to servers on the same local subnet; servers on the local net
are given the second strongest preference. Therefore, if you configure
multiple servers on both sides of a gateway, a server on the same side of
the gateway as the NFS client is always used.
Among servers that are equally far away, response time determines the
order, if no weighting factors are used. Multiple servers give users
reliable access to a mounted directory because if one server is down, the
directory can be mounted from another. In addition, multiple servers
provide some load balancing across the network; a server that is not busy
responds more quickly to AutoFS poll than the one that is heavily loaded.
Therefore, the directory is mounted from a server that is not busy.
If the list of multiple servers contains some servers using the NFS
Version 2 Protocol and some servers using the NFS Version 3 Protocol,
AutoFS chooses a subset of the list having only servers with the same
protocol. This subset is formed of servers using the NFS Version 3
Protocol, unless there are no such servers on the list, or there is a server
using NFS Version 2 Protocol that has the strongest preference.