Installation guide

Chapter 9.
Setting Up a Red Hat Enterprise Linux LVS
Cluster
A Red Hat Enterprise Linux LVS cluster consists of two basic groups: the LVS routers and
the real servers. To prevent a single point of failure, each groups should contain at least
two member systems.
The LVS router group should consist of two identical or very similar systems running Red
Hat Enterprise Linux. One will act as the active LVS router while the other stays in hot
standby mode, so they need to have as close to the same capabilities as possible.
Before choosing and configuring the hardware for the real server group, you most decide
what which of the three types of LVS topographies to use.
9.1. The NAT LVS Cluster
The NAT topography allows for great latitude in utilizing existing hardware, but it is limited
in its ability to handle large loads due to the fact that all packets going into and coming out
of the cluster pass through the LVS router.
Network Layout
The topography for an LVS cluster utilizing NAT routing is the easiest to configure
from a network layout perspective because the cluster needs only one access point to
the public network. The real servers pass all requests back through the LVS router so
they are on their own private network.
Hardware
The NAT topography is the most flexible in regards to cluster hardware because the
real servers do not need to be Linux machines to function correctly in the cluster. In a
NAT cluster, each real server only needs one NIC since it will only be responding to
the LVS router. The LVS routers, on the other hand, need two NICs each to route traffic
between the two networks. Because this topography creates a network bottleneck at
the LVS router, gigabit Ethernet NICs can be employed on each LVS router to increase
the bandwidth the LVS routers can handle. If gigabit Ethernet is employed on the LVS
routers, any switch connecting the real servers to the LVS routers must have at least
two gigabit Ethernet ports to handle the load efficiently.
Software
Because the NAT topography requires the use of iptables for some configurations,
there can be a fair amount of software configuration outside of Piranha Configu-