HP XC System Software Administration Guide Version 2.1

1.6 Networking
The H P XC system uses the Linux Virtual Server (LVS), Network Time Protocol (NTP),
Network Address Translation (NAT), and Network Information Service (NIS).
1.6.1 Linux Virtual Server (LVS) for HP XC System Alias
The HP XC system uses the Linux Virtual Server (LVS) to present a single host name for user
logins. LVS is a highly scalable virtual server built on a cluster of real servers. By using LVS,
the architecture of t he HP XC system is transparent to end users, and they see only a single
virtual server. This eliminates the need for users to kno w how the cluster is configured in
order to successfully log in and use the cluster. Any changes in the system configuration are
transparent to end users. LVS also provides load b alancing across login nodes, which distributes
login requests to different servers. Figu re 1-1 illustrat es the use of LVS in an H P XC system.
Figure 1-1: LVS View of Cluster
User
LVS
Single System View of Cluster
HP XC Cluster
1.6.2 Network Time Protocol
One node in an HP XC system acts as the internal Network Time Protocol (NTP) server for all
the other nodes. By default this is the head node. All o ther nodes are NTP clients of this server.
You can specify where the internal NT P server gets the tim e. You can specify up to three
external time sources if the internal server has a connection to an outside network. You can also
choose to use the internal server’s own clock as the time source.
Should som e th ing go wrong and you notice a problem with the clocks synchroni zing on any
nodes, check the internal server’s /etc/ntp.conf file and the ntp.conf file on the nod es
that are experiencin g the problem.
Other tools, such as ntpq and ntpdc, are also available. See the m anual pages for ntpd
(1),
ntpq
(1), ntpdc(1),andntp.conf.
1-8 HP XC Administrative Environment