.SAN design reference guide Vol. 1-5 785350-001

Interoperable, heterogeneous switch fabrics
An interoperable, heterogeneous switch fabric can contain different series of switches.
Table 75 (page 162) lists the switch combinations.
Table 75 Heterogeneous switches in the same fabric
Reference
Heterogeneous switch
combinations
Fabric Interoperability: Merging Fabrics Based on C-series and B-series Fibre Channel
Switches Application Notes
C-series and B-series
The document referenced in Table 75 (page 162) is available on the HP SAN Infrastructure website:
http://www.hp.com/go/SDGManuals
Third-party switch support
HP Services offers support for certain third-party switches if you purchase third-party support through
Multivendor Environment Services. For more information, see the HP Storage Services website:
http://www8.hp.com/us/en/services/services-detail.html?
pageTitle=Integrated-Multivendor-Services&compURI=tcm%3A245-807609&
jumpid=reg_R1002_USEN
HP Services also offers support for multivendor SANs. HP provides integrated hardware and
software support with proactive problem prevention and 24x7 assistance.
SAN performance considerations
The following SAN components affect SAN application performance:
• Host CPUs
• Fibre Channel HBAs
• SAN topology and the number of fabrics
• I/O transfer sizes and usage patterns
• RAID controllers
• Disk configuration
Infrastructure factors
A single-switch fabric provides the highest level of performance. In a fabric with multiple switches,
the following factors can affect performance:
• Latency
Switch latency is less than 5% (at 1 Gb/s) of the data transfer time; therefore, the number of
switches and hops between devices is not a major performance factor. However, as devices
send frames through more switches and hops, other data traffic in the fabric routed through
the same ISL or path can cause oversubscription.
• Oversubscription
Oversubscription degrades Fibre Channel performance. When devices must contend for the
same ISL or path, each device receives an equal share or 1/nth of the available bandwidth
on the path (where n is the number of contending devices). Oversubscription occurs when
one or more devices sends more data than the total bandwidth available on the ISL or path.
• Fabric interconnect speeds
Fibre Channel supports 16 Gb/s, 8 Gb/s, 4 Gb/s, 2 Gb/s, and 1 Gb/s speeds. For optimum
performance, configure a fabric with all components at the same, highest available speed.
162 SAN fabric connectivity and switch interoperability rules