HP StorageWorks SAN Virtualization Services Platform administrator guide (5697-0204, January 2010)

11 Configuration best practices
Best configuration practices are the recommended and field tested approach to configuring SVSP.
These best configuration practices are formulated to enable SVSP storage administrators to create
and operate an environment that does not require constant attention to assure that all components
are operating without congestion and below saturation. These practices also allow operations to
continue within a defined performance range when a component fails, and can be used to set
performance expectations for performance while a component is serviced.
SAN topology
SVSP must be installed into SANs that are reliable and have sufficient amounts of available Fibre
Channel (FC) network capacity and bandwidth to support the added requirements of SVSP. For
example, the SVSP Data Path Modules should be considered high bandwidth devices and therefore
need to be attached to core or director class FC switches. In addition, any path from a server, through
the DPMs, to the back-end storage, must be free of congestion and not over subscribed. The following
sections mention some best practices for good SAN design which avoids creating congestion.
Redundant fabrics
SVSP must be deployed into SANs that consist of dual-redundant fabrics as defined in the HP SAN
Design Guide (http://www.hp.com/go/sandesignguide). Using any logical separation in a single
SAN fabric will not deliver the isolation and availability necessary in a production environment. HP
recommends that the two fabrics be constructed so they are easy to understand and troubleshoot. For
example, the cable and port assignment scheme could be designed to use mirror image or point
symmetry.
SAN switches
All switches on a fabric must be from the same vendor. It is supported for one fabric to contain switches
from one vendor and the other fabric to contain switches from a different vendor. Switches are not
supported in vendor neutral roles (or interoperability mode).
High bandwidth devices (such as tape backup servers and storage arrays) often use the same SAN
switches as the SVSP components. Because the VSMs also perform data movement tasks, they should
also be considered a high bandwidth device.
Fibre Channel links
Congestion occurring in FC is likely to cause problems because the protocol does not provide effective
mechanisms for relieving the congestion. Problems on a congested link or fabric can range anywhere
from slow response times to discarded I/O to loss of access to the fabric. Any link that has the potential
for “fan-in,” where multiple links funnel into a single link, or a smaller number of links can become
overloaded. The most well known examples are ISLs (inter-switch links).
Take peak loads into account and add some margin above and beyond that number. It cannot be
reiterated enough that once a FC link becomes saturated or congested, major changes may be required
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