always on, multi-site design considerations
TRANSCRIPT
John Q MartinSales Engineer
Multi-Site Always On Design Considerations
About Me John Q Martin Sales Engineer for SQL Sentry
Over ten years experience with SQL Server
Previously worked as a DBA, SQL Dev, BI Dev
Worked as a SQL Server Premier Field Engineer (PFE) for Microsoft in the UK
Twitter : @SQLDiplomatEmail : [email protected] : http://blogs.sqlsentry.com/author/JohnMartin/
E-Mail [email protected] for free copies of our $10 e-books.
Tuning blog: http://www.sqlperformance.com/
What is Always On? Always On is a set of features
Failover Cluster Instances (FCI)
Availability Groups
Availability Groups Database Level Protection
Local Storage
Multiple Replicas
Failover Cluster Instances Instance Level Protection
Shared Storage
Single Database Replica
Why Multi-site?Improved Resilience
High Availability and Disaster Recovery
Service Versatility & Flexibility
RPO and RTO requirements
Multi-site HA Vs DR
Before you start on the multi-site road, understand what your
objective is. Are you looking for Multi-Site High Availability or a
Disaster Recovery option.
Multi-Site Considerations
Storage LayoutNetwork ConnectivitySoftware Versions in useClient Application Design
Storage Configurations
Failover Cluster Instances• SAN Replication
Failover Cluster Instance
Image Source: Windows Server 2008 Multi-Site Clustering Technical Decision-Maker White Paper, November 2007
Storage Configurations
Availability Groups• Local Storage
Image Source: Overview of AlwaysOn Availability Groups (SQL Server) [MSDN]
Network Connectivity Latency Can Hurt
Multiple IP SubnetsClustering Network Config
Network Connectivity Latency Can Hurt
Multiple IP SubnetsClustering Network Config
Site 1 Site 2
Update
Transaction Log Transaction Log
Network Connectivity Latency Can Hurt
Multiple IP SubnetsClustering Network Config
Site 1 Site 2
Transaction Log Transaction Log
Update
Network Connectivity Latency Can Hurt
Multiple IP SubnetsClustering Network Config
Site 1 Site 2
Transaction Log Transaction Log
Update
Network Connectivity Latency Can Hurt
Multiple IP SubnetsClustering Network Config
Site 1 Site 2
Transaction Log Transaction Log
Update
Network Connectivity Latency Can Hurt
Multiple IP SubnetsClustering Network Config
Site 1 Site 2
Transaction Log Transaction Log
Update
Network Connectivity Latency Can Hurt
Multiple IP SubnetsClustering Network Config
Site 1 Site 2
Transaction Log Transaction Log
Local Latency
Remote Latency
Update
Network Connectivity Latency Can Hurt
Multiple IP SubnetsClustering Network Config
Site 1 Site 2
Transaction Log Transaction Log
Local Latency
Remote Latency
UpdateCommit
Cluster Network Configuration
What and where to change.
Demo Code: Cluster DNS Config
## // Set Parameters for the network name you want to modify the DNS behavior for$clusterName = "sqllabcl01"$clusterGroupName = "SqlLabAg01"$clusterResourceType = "Network Name"
## // 0 / False = Register only the active IP Address for the network name## // 1 / True = Register all possible IP Addresses for the network name$ipRegistrationSetting = $false
## // Set reduced TTL (seconds) for DNS Records to use when not registering all network IP addresses$ttlValue = 30
## // If reverting to use all IP addresses then revert TTL for DNS to defaultif($ipRegistrationSetting){ $ttlValue = 1200}
## // Set the Register All Providers IP Address parameterGet-Cluster -Name $clusterName | ` Get-ClusterGroup -Name $clusterGroupName | ` Get-ClusterResource | Where-Object {$_.ResourceType -eq $clusterResourceType} | ` Set-ClusterParameter -Name RegisterAllProvidersIP -Value $ipRegistrationSetting
Demo Code: Cluster DNS Config (cont.)
## // Set the Register All Providers IP Address parameterGet-Cluster -Name $clusterName | ` Get-ClusterGroup -Name $clusterGroupName | ` Get-ClusterResource | Where-Object {$_.ResourceType -eq $clusterResourceType} | ` Set-ClusterParameter -Name RegisterAllProvidersIP -Value $ipRegistrationSetting
## // Set the TTL value appropriately for the configurationGet-Cluster -Name $clusterName | ` Get-ClusterGroup -Name $clusterGroupName | ` Get-ClusterResource | Where-Object {$_.ResourceType -eq $clusterResourceType} | ` Set-ClusterParameter -Name HostRecordTTL -Value $ttlValue
## // Stop the network name resourceGet-Cluster -Name $clusterName | ` Get-ClusterGroup -Name $clusterGroupName | ` Get-ClusterResource | Where-Object {$_.ResourceType -eq $clusterResourceType} | ` Stop-ClusterResource
## // Start the network name resourceGet-Cluster -Name $clusterName | ` Get-ClusterGroup -Name $clusterGroupName | ` Get-ClusterResource | Where-Object {$_.ResourceType -eq $clusterResourceType} | ` Start-ClusterResource
Demo Code: Cross-Subnet settings
# PowerShell Code# Specify the cluster name you want to set the values for$clusterName = "SqlLabCL01"# Specify values$crossSubDelay = 1000 # Min: 250, Max 4000$crossSubThreshold = 5 # Min: 2, Max 120
## Calculation for how long a node can be disconnected."Network Failure Tolerance: " + (($crossSubDelay/1000) * $crossSubThreshold).ToString() + " seconds."
$cluster = Get-Cluster -Name $clusterName
# Frequency that heartbeat is sent in ms$cluster.CrossSubnetDelay = $crossSubDelay# Number of missed heartbeats$cluster.CrossSubnetThreshold = $crossSubThreshold
## Current valuesget-cluster |` select CrossSubnetDelay, CrossSubnetThreshold, SameSubnetDelay, SameSubnetThreshold | ` Format-List
Quorum Configurations
It Depends
Software Versions Windows Server
• 2008 SP2 & Above*
SQL Server Enterprise Ed.• 2012 & Above
Application Design Allow for Latency
• Caching, Queuing etc.
Unreliable Connections• Retry Logic
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