Information Technology Reference
In-Depth Information
We'll start with a quick review of NLB clustering and how you can use it in your vSphere
environment.
Introducing Network Load Balancing Clustering
The Network Load Balancing coni guration involves an aggregation of stateless servers that
balances the requests for applications or services. In a typical NLB cluster, all nodes are active
participants in the cluster and are consistently responding to requests for services. If one of
the nodes in the NLB cluster goes down, client connections are simply redirected to another
available node in the NLB cluster. NLB clusters are most commonly deployed to enhance per-
formance and availability. Because client connections could be directed to any available node
within the cluster, NLB clusters are best suited for scenarios involving stateless connections and
protocols, such as environments using Microsoft Internet Information Services (IIS), virtual pri-
vate networking (VPN), or Microsoft Internet Security and Acceleration (ISA) Server, to name a
few. Figure 7.2 summarizes the architecture of an NLB cluster made up of Windows-based VMs
(the architecture is the same for physical systems).
Figure 7.2
An NLB cluster
can contain up to
32 active nodes
(only 5 are shown
here), and tra c is
distributed equally
across each avail-
able node. h e NLB
software allows
the nodes to share
a common name
and IP address that
is referenced by
clients.
VM1
VM2
VM3
VM4
VM5
Load-balanced identity: www.lab.local (1 0.1.1.10)
Network Load-Balancing Support from VMware
As of this writing, VMware supports NLB, but you will need to run NLB in Multicast mode to sup-
port vMotion and VMs on diff erent physical hosts. You will also need to confi gure static Address
Resolution Protocol (ARP) entries on the physical switch to achieve this, which greatly limits the
scalability of the solution. If NLB is running in Unicast mode, then the VMs will all need to be
running on the same host, which is generally not a good idea if you want high availability! Another
option to consider would be third-party load balancers to achieve the same results.
NLB clusters aren't the right i t for every application or workload. For applications and work-
loads that aren't a good i t for NLB, Microsoft offers Windows Server Failover Clustering.
 
Search WWH ::




Custom Search