Using Multiple Subnets; Using Mpio With Multiple Subnets; Multi-Site San Mapping To Subnets, Vips, And Application Servers - HP StorageWorks P4000 User Manual

Using multiple subnets

You can use multiple subnets with a Multi-Site SAN. Multiple subnets let you have multiple VIPs, one
VIP per subnet. The advantage of using multiple VIPs is that you can connect to a volume without
having to leave the local subnet.
Alternatively, you can assign an application server to a site. Application servers assigned to a site
connect only to storage systems in the same site. For more information, see
implementing the Multi-Site SAN
If you use multiple subnets within the iSCSI cluster and implement one subnet per site, you can take
advantage of the following Multi-Site SAN features:
One Virtual IP address per site. iSCSI discovery sessions are terminated on a storage system that
is local to the application server in that site.
Virtual IP addresses are hosted only on storage systems that reside in the same subnet as the VIP.
Read and Write I/O requests are forwarded from the application server to a storage system that
is in the same site as the server. This ensures that the I/O path is optimal and multiple network
hops across the network link between the sites are eliminated.
Figure 11 on page 18 shows an example of how the Multi-Site SAN setup maps to subnets, VIPs, and
application servers.
1. Dual redundant GigE links
Figure 11 Multi-Site SAN mapping to subnets, VIPs, and application servers
.

Using MPIO with multiple subnets

When you are using multiple subnets in a Multi-Site SAN, the HP StorageWorks P4000 DSM or
Microsoft DSM will only build I/O paths to the storage systems that are in the same subnet as the
application server. See the HP StorageWorks P4000 Windows Solution Pack User Manual for more
information about MPIO.
18 Designing a Multi-Site SAN
network" on page 14.
"Best practices for