.Part 5 Storage Security Best Practices and Support Information HP SAN Design Reference Guide 785355-001

Data access patterns
Review your data access needs before making a topology choice. The optimum SAN configuration
depends on I/O traffic requirements and data access patterns:
• Local (one-to-one)—Data access between a local server and a storage system connected to
the same switch
• Centralized (many-to-one)—Data access between multiple, dispersed servers and one centrally
located storage system
• Distributed (many-to-many)—Data access between multiple, dispersed servers and storage
systems
For recommended topologies based in the primary data access type, see “Data access performance
by SAN fabric topology” (page 33).
ISL ratio
Determine the ISL ratio for switch-to-switch connectivity based on the workload of servers and
storage systems. In some cases, you can assess the I/O requirements of your applications and
servers by using application sizing tools. After deployment, use current system measurements to
determine the actual workload, and modify your implementation if the initial design does not meet
your requirements. For more information, see “Recommended ISL ratios” (page 31).
Incremental SAN expansion
Plan for expansion when the initial design is a subset of a future, larger design. For example, if
you are using a core-edge topology in the initial design, allocate spare ports on the core switches
to support addition of edge switches.
To expand the SAN, you can make incremental changes rather than reconfiguring the entire SAN.
Changes to the core switches are isolated from the edge switches, which minimizes the effect of
changes required to support core growth. Changes to the server connection to an edge switch are
isolated from the core, which minimizes the effect of server-related changes. If you are using two
or more fabrics, you can temporarily route server I/O traffic to one fabric while the other fabric
is being modified.
SAN configuration
After completing the planning phase, you can configure your SAN. During the configuration phase,
record details about the physical configuration.
To facilitate maintenance, observe the following practices:
• Record keeping
Record the cable connections on the configuration layout diagram. Record the WWN and
location of each node and device.
• HBA labels
Affix a label on each HBA that clearly identifies the WWN. HP storage systems are prelabeled
with this information. Affix another label in plain view if necessary.
• Cable labels
Label both ends of each cable with a cable number or color-coding scheme. This allows you
to quickly identify each cable. Securely affix a label to each end of the cable to identify
connection points, such as TO and FROM.
• Switch ports
Use port plugs to protect unused switch ports; never leave ports exposed.
SAN configuration 385