HP StorageWorks 2/140 FW 08.01.00 McDATA Products in a SAN Environment Plannin - Page 121

Fabric Availability Planning Considerations for Fibre Channel Topologies 3 • 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. 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. Fibre Channel fabrics are classified by four levels of resiliency and redundancy. From least available to most available, the classification levels are: • Nonresilient single fabric - Directors and switches are connected to form a single fabric that contains at least one single point of failure (fabric element or ISL). Such a failure causes the fabric to fail and segment into two or more smaller fabrics. Planning Considerations for Fibre Channel Topologies 3-37