FW 05.01.00 and SW 07.01.00 HP StorageWorks SAN High Availability Planning Guide (AA-RS2DC-TE, June 2003)

Planning Considerations for Fibre Channel Topologies
104 SAN High Availability Planning Guide
■ 11 to 1 fan-out region — Eleven NT servers with I/O capabilities of 10
MBps and 1,000 IOPS are fabric-attached through a 32-port edge switch. The
primary applications are e-mail and online transaction processing (OLTP).
Because bandwidth use is light and noncritical, the servers are connected to
the core director with a single ISL that is intentionally oversubscribed (1.1
Gbps plus Class F traffic). The servers are connected to storage devices with
I/O capabilities of 11,000 IOPS.
■ 6 to 1 fan-out region — Six servers with I/O capabilities of 20 MBps and
1,500 IOPS are fabric-attached through a 16-port edge switch. Bandwidth use
is light to medium but critical, so the servers are connected to the core director
with two ISLs (0.6 Gbps each plus Class F traffic). The servers are connected
to storage devices with I/O capabilities of 9,000 IOPS.
■ 3 to 1 fan-out region — Three servers with I/O capabilities of 30 MBps and
2,000 IOPS are fabric-attached through a 16-port edge switch. Bandwidth use
is medium but non-critical, so the servers are connected to the core director
with one ISL (0.9 Gbps plus Class F traffic). The servers are connected to
storage devices with I/O capabilities of 6,000 IOPS.
Fabric Availability
Many fabric-attached devices require highly available connectivity to support
applications such as disk mirroring, server clustering, or business continuance
operations. High availability is accomplished by deploying a resilient fabric
topology or redundant fabrics.
A fabric topology that provides at least two internal routes between fabric
elements is considered resilient. A single director, switch, or ISL failure does not
affect the remaining elements and the overall fabric remains operational.
However, unforeseen events such as human error, software failure, or disaster can
cause the failure of a single resilient fabric. Using redundant fabrics (with
resiliency) mitigates these effects and significantly increases fabric availability.