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Transcript of Multi Site Cluster
7/27/2019 Multi Site Cluster
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ImplementingMulti-Site Clusters
April 14 20111
Trần Văn Huệ Nhất Nghệ CPLS
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Overview of Multi-Site Clusters
•What Are Multi-Site Clusters?
•What Makes Multi-Site Clusters Unique?
•Why Use a Multi-Site Cluster?
• Evaluating the Business Need for a Multi-Site Cluster
•Storage Challenges for Multi-Site Clusters
•Synchronous / Asynchronous Replication?
•
Network Challenges for Multi-Site Clusters • Choosing the Appropriate Quorum Mode in Multi-Site Clusters
• Demo: Deploying a Multi-Site Cluster
Agenda:
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What Are Multi-Site Clusters?
A multi-site cluster is a cluster that has been extended so that
different nodes in the same cluster reside in separatephysical locations
Site A Site B
SAN SAN
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What Makes Multi-Site Clusters Unique?
• Multiple storage arrays, which are independent in each site
• Nodes commonly access storage local to their own sites
• Storage is replicated between sites
• No “true” shared disk is visible to all nodes
Site A Site B
Changes aremade on Site Aand replicated
to Site B
Replica
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Why Use a Multi-Site Cluster?
Advantages over cold standby server in a disasterrecovery site:
Automatic failover • Reduced downtime
• Lower complexity
Reducedadministrativeoverhead
•
Automatic synchronization of applicationand cluster changes
• Better service continuity than coldstandby servers
Reduced human
error factor
• Reduced reliance on old, potentially
error-prone procedures
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Evaluating the Business Need for a Multi-Site Cluster
• Because of increased cost and complexity, multi-siteclusters aren’t for every company or application
• Evaluate the application type and importance, and consider
available alternatives
• Plan for the application and hardware architecture, andfor routine failover and failback testing
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Storage Challenges for Multi-Site Clusters
Challenge Description
Requires aseparate orthird-party datareplicationsolution
• Hardware (block level) storage-basedreplication
• Software (file system level) host-basedreplication
• Application-based replication (such asExchange 2007 Cluster ContinuousReplication)
Can be eithersynchronous orasynchronousreplication
•Synchronous: No acknowledgement of datachanges made in Site A until the data issuccessfully written to Site B
• Asynchronous: Data changes made in SiteA will eventually be written to the storagein Site B
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What Is Synchronous Replication?
When you use synchronous replication, the host receives a
“write complete” response from the primary storage after thedata is written successfully to both storage locations
PrimaryStorage
Secondary
Storage
WriteRequest
WriteComplete
Replication
Acknowledgement
Data Data
Site A Site B
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What Is Asynchronous Replication?
When you use asynchronous replication, the host receives a
“write complete” response from the primary storage after thedata is written successfully on the primary storage
PrimaryStorage
Secondary
Storage
WriteRequest
WriteComplete
Replication
Data Data
Site A Site B
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Comparing Synchronous and AsynchronousReplication
Replication Type Description
Synchronous • Works across shorter distances
• Results in no data loss
• Requires high-bandwidth/low-latencyconnections
• Allows write latencies to impactperformance
Asynchronous • Stretches over longer distances
• Results in potential data loss on hard
failure• Assumes large enough bandwidth to keep
up with data
• Does not significantly impact performance
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Network Challenges for Multi-Site Clusters
• Inter-node communications are time sensitive; you mightneed to configure these thresholds to meet the higherWAN latency
• DNS replication might impact client reconnect times when
failover is based on hostname
• Some applications might require all of the nodes to be in the
same Active Directory site
• Active Directory replication latency might effect applicationdata availability
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Choosing the Appropriate Quorum Mode inMulti-Site Clusters
Quorum Mode Choose when:
Node and DiskMajority
• Directed by vendor only
No Majority: DiskOnly
• Directed by vendor only
Node Majority • Limited to two sites
Node and File ShareMajority
• Three sites are available
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Using Node and File Share Majority in aMulti-Site Cluster
• File share witness allows a 2-node cluster with no shared disk
• Single file server can serve as the witness for multiple clusters
Third-Party Replication
Mechanism
Site C File ShareWitness
SAN
Site A Site B
SAN
WAN
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Deploying a Multi-Site Cluster
When deploying multi-site clusters:
Ensure that the business requirements are met bythe solution
Use a hardware vendor to create a full solution for
multi-site clusters
Choose the correct quorum mode to properly maintainfunctionality in the event of failures
Choose the correct storage replication solution to meet
these needs
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Demo
Demo:Multi Site Cluster
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Demo
Private network: 172.16.1.0/16
Public network: 192.168.1.0/24
PC08: DC, QuorumIP: 192.168.1.8
Datakeeper replicate
PC09:IP: 192.168.1.9IP: 172.16.1.9
PC10:IP: 192.168.1.10IP: 172.16.1.10
Site 1Site 2
Site 3