HP StorageWorks 2/140 FW 08.01.00 McDATA Products in a SAN Environment Plannin - Page 179
Extended-Distance Operational Modes, Extended-Distance, Operational Modes
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Implementing SAN Internetworking Solutions 4 • 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 besteffort 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 SAN Extension Transport 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 Extended-Distance Operational Modes) and transport technology (described in SAN Extension Transport 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 • Recovery point objective (RPO) - The RPO is the time between backup points and defines how far out of date a backup copy can be after a failure.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. Extended-Distance Operational Modes A primary component of business continuance and disaster recovery is remote data replication to an alternative safe location. Extendeddistance operational modes are: Implementing SAN Internetworking Solutions 4-37