HP StorageWorks 2/140 FW 08.01.00 McDATA Products in a SAN Environment Plannin - Page 115

Planning Considerations for Fibre Channel Topologies 3 I/O Requirements • Software limits, including the maximum number of fabric elements managed by the SAN management application and the maximum number of zones and zone members. For additional information, refer to SAN Management Applications and Configuring Zones. McDATA directors and fabric switches are designed with nonblocking architecture; therefore any two switch ports can communicate at the full Fibre Channel bandwidth of 1.0625, 2.1250, 4.2500, or 10.2000 Gbps without impact to other switch ports. Because most SAN-attached devices are not capable of generating I/O traffic at the full bandwidth, there is little potential for congestion between two devices attached through a single director or switch. However, when multiple directors or switches are connected through a fabric ISL that multiplexes traffic from several devices, significant potential for congestion arises. To minimize congestion, factors such as application I/O profiles, ISL oversubscription, and device locality must be included in the fabric design. Application I/O Profiles Understanding application I/O characteristics is essential to SAN, fabric, and ISL design. Factors that may affect application I/O include: • Read/write mixture - Although application I/O is typically a mixture of read and write operations, some applications are very biased. For example, video server applications are almost 100% read intensive, while real-time video editing applications are mostly write intensive. Read operations typically take less time than write operations, therefore storage devices for a read-intensive application usually wait for data transfer. As a consequence, read-intensive applications typically require high bandwidth to the device. • Type of data access - When an application requires data, access to that data is random or sequential. For example, e-mail server activity is random access, while seismic data processing for the oil and gas industry is sequential access. Sequential data access typically takes less time than random data access, therefore sequential-access applications usually wait for data transfer. As a consequence, sequential-access applications typically require high bandwidth to the device. Planning Considerations for Fibre Channel Topologies 3-31