3.7.0 HP StorageWorks HP Scalable NAS File Serving Software administration guide - HP Scalable NAS 3.7 for Linux (AG513-96002, October 2009)

name of the server to the virtual host, which is generally the better solution, or keep
the published name associated with the server.
• Migrate the existing server name to a virtual hostname. In this case, you will need
to assign a new name to the server. External sites that then access the original
server name will actually be served by the virtual host—basically, a failover-pro-
tected version of the server, with no difference in appearance to the clients.
• Keep the existing name on the server. If you do not rename the server, clients will
need to use the new virtual host name to benefit from failover protection. Clients
can still access the server by its name, but those requests are not protected by
HP Scalable NAS. If the server fails, requests to the server’s hostname fail,
whereas requests to the new virtual hostname are automatically redirected by HP
Scalable NAS to a backup server.
Configure servers for DNS load balancing
HP Scalable NAS can provide failover protection for servers configured to provide
domain name service (DNS) load balancing. DNS load balancing allows you to set
up servers so that requests are sent alternately to each of the servers in a cluster. For
example, clients could access acmd1 and acmd2 in turn, enabling the servers to
share the load of accepting and responding to client requests.
DNS includes a round-robin feature using address records (A records) to alternate
requests between IP addresses. This feature provides a straightforward way to gain
load balancing capability and simplified load balancing, resulting in improved
response time.
HP Scalable NAS provides failover protection for this configuration. Without HP
Scalable NAS, requests are simply alternated between the servers. If a server goes
down, requests to that server do not connect.
To configure round-robin load balancing with HP Scalable NAS, first define virtual
hosts as addresses in the A records on the DNS. Then use HP Scalable NAS to
associate primary and backup servers with that virtual host. In essence, you use the
virtual host capability of HP Scalable NAS to accept the round-robin requests sent
by the DNS. HP Scalable NAS handles the failover function to the real servers in the
cluster. In the following example, two servers, acmd1 and acmd2, are configured
to accept round-robin requests.
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