Administrator Guide

Integrity and resiliency
This chapter describes how the high availability and the redundancy features of metro node provide robust system integrity and
resiliency.
Topics:
• About metro node resilience and integrity
• Site distribution
• Cluster
• Metadata volumes
• Backup metadata volumes
• Logging volumes
• High availability and metro node hardware
• Metro node Metro Hardware
About metro node resilience and integrity
With metro node, you get true high availability. Operations continue and data remains online even when a failure occurs.
Within synchronous distances (metro node Metro), think of metro node as providing disaster avoidance instead of just disaster
recovery.
Metro node Metro provides shared data access between sites. The same data (not a copy), exists at more than one location
simultaneously. metro node can withstand a component failure, a site failure, or loss of communication between sites and still
keep the application and data online and available. Metro node clusters are capable of surviving any single hardware failure in
any subsystem within the overall storage cluster, including host connectivity and memory subsystems. A single failure in any
subsystem does not affect the availability or integrity of the data.
Metro node redundancy creates fault tolerance for devices and hardware components that continue operation as long as one
device or component survives. This highly available and robust architecture can sustain multiple device and component failures
without disrupting service to I/O.
Failures and events that do not disrupt I/O include:
● Unplanned and planned storage outages
● SAN outages
● Metro node component failures
● Metro node cluster failures
● Data center outages
To achieve high availability, you must create redundant host connections and supply hosts with multi path drivers.
NOTE:
In the event of a front-end port failure or a director failure, hosts without redundant physical connectivity to a
metro node cluster and without multi-pathing software installed could be susceptible to data unavailability.
Site distribution
When two metro node clusters are connected together with metro node Metro, metro node gives you shared data access
between sites. Metro node can withstand a component failure, a site failure, or loss of communication between sites and still
keep the application and data online and available.
Metro node Metro ensures that if a data center goes down, or even if the link to that data center goes down, the other site can
continue processing the host I/O.
In the following figure, despite a site failure at Data Center B, I/O continues without disruption in Data Center A.
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