Server Cluster; Nlb - HP Rx2620-2 - Integrity - 0 MB RAM Installation And Configuration Manual

Table 1-1 Server Cluster and NLB Features (continued)

Server Cluster

Supports clusters up to eight nodes
Requires the use of shared or replicated storage
Server Cluster
Use a server cluster to provide high availability for mission critical applications through failover.
It uses a shared-nothing architecture, which means that a resource can be active on only one
node in the cluster at any given time. Because of this, it is well suited to applications that maintain
some sort of fixed state (for example, a database). In addition to database applications, enterprise
resource planning (ERP), customer relationship management (CRM), online transaction processing
(OLTP), file and print, email, and custom application services are typically clustered using server
cluster.
When you deploy a server cluster, first configure the two to eight servers that will act as nodes
in the cluster. Then configure the cluster resources that are required by the application you are
clustering. These resources can include network names, IP addresses, applications, services, and
disk drives. Finally, bring the cluster online so that it can begin processing client requests.
Most clustered applications and their associated resources are assigned to one cluster node at a
time. If a server cluster detects the failure of the primary node for a clustered application, or if
that node is taken offline for maintenance, the clustered application is started on a backup cluster
node. Client requests are immediately redirected to the backup cluster node to minimize the
impact of the failure.
NOTE: Though most clustered services run on only one node at a time, a cluster can run many
services simultaneously to optimize hardware utilization. Some clustered applications can run
on multiple Server Cluster nodes simultaneously, including Microsoft SQL Server.

NLB

Use NLB to provide high availability for applications that scale out horizontally and do not
maintain a fixed state, such as web servers, proxy servers, and other services that need client
requests distributed across nodes in a cluster. NLB uses a load balancing architecture, which
means that a resource can be active on all nodes in the cluster at any given time.
NLB clusters do not use a quorum, and so they don't impose storage or network requirements
on the cluster nodes. If a node in the cluster fails, NLB automatically redirects incoming requests
to the remaining nodes. If you take a node in the cluster offline for maintenance, you can use
NLB to allow existing client sessions to finish before taking the node offline. This eliminates any
end-user impact during planned downtime. NLB can also weigh requests, which enables you to
mix high-powered servers with legacy servers and ensure all hardware is efficiently used.
Most often, NLB is used to build redundancy and scalability for firewalls, proxy servers, or web
servers, as illustrated in
virtual VPN endpoints, streaming media servers, and Terminal Services.
For more information about the key features of this technology and its internal architecture and
performance characteristics, go to:
http://technet2.microsoft.com/WindowsServer/en/library/
98d46a24-96d8-412c-87d8-28ace62323d21033.mspx?mfr=true
NLB
Supports clusters up to 32 nodes
Doesn't require any special hardware or software
Figure 1-1. Other applications commonly clustered with NLB include
Server Cluster Versus Network Load Balancing 13