Extended-Distance Operational Modes - McDATA StorageWorks 2/140 - Director Switch Planning Manual

Extended-Distance
Operational Modes
• Reliability - Local storage traffic requires high-reliability
communication and is intolerant of data loss, out-of-order packet
receipt, or data retransmission. WANs typically provide best-
effort communication service and rely on upper-level protocols
for end-to-end transport.
Because of these differences, a protocol conversion approach is
usually required to integrate Fibre Channel SAN traffic over a
geographically-dispersed network. Refer to
Technologies for detailed information about native FCP distance
extension or protocol conversion.
Other BC/DR requirements vary, depending on budget, data type,
data volume, business situation, and SAN applications. Analyze and
understand these business requirements prior to selecting an
operational mode (described in
and transport technology (described in
Technologies) that best support the SAN distance-extension strategy. In
particular, consider:
• Data priority - Not all data is critical to immediate business
resumption. Prioritize and categorize data as mission-critical,
secondary, or only to be retained for legal purposes.
• Recovery time objective (RTO) - The RTO is the time required to
restore the data and applications following an outage or disaster.
The loss of revenue from suspended business operations drives
this objective.
• Recovery point objective (RPO) - The RPO is the time between
backup points and defines how far out of date a backup copy can
be after a failure. The data rate of change and cost of destroyed
data (between the last backup and a disaster) drive this objective.
• Distance - The distance between a data center and replication site
is proportional to RTO and RPO times. As distance between sites
increases, time required to perform backup and restore operations
also increases.
A primary component of business continuance and disaster recovery
is remote data replication to an alternative safe location. Extended-
distance operational modes are:
Implementing SAN Internetworking Solutions
SAN Extension Transport
Extended-Distance Operational
SAN Extension Transport
Implementing SAN Internetworking Solutions
4
Modes)
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