Site A But what if there is a catastrophic event? Fire, flood, earthquake … Same Physical Location

Site B Site A Applications are failed over to a separate physical location Node is moved to a physically separate site

The primary reason DR solutions fail is dependence on people The primary reason DR solutions fail is dependence on people

Site A Public Network Site B Separate Network

Site A Site B

OR Network Name resource IP Address Resource A IP Address Resource A IP Address Resource B IP Address Resource B

DNS Server 1 DNS Server 2 DNS Replication Record Updated Record Created Record Obtained FS = Record Updated FS = Site ASite B

DNS Server 1 DNS Server 2 FS = Site ASite B

DNS Server 1 DNS Server 2 FS = Site ASite B VLAN

DNS Server 1 DNS Server 2 FS = Site ASite B

Site A Site B

Site A Changes are made on Site A and replicated to Site B Site B Replica Need a data replication mechanism between sites

Primary Storage Secondary Storage Write Complete Replication Acknowledgement Write Request

Primary Storage Secondary Storage Write Complete Replication Write Request

SynchronousAsynchronous No data lossPotential data loss on hard failures Requires high bandwidth/low latency connection Enough bandwidth to keep up with data replication Stretches over shorter distances Stretches over longer distances Write latencies impact application performance No significant impact on application performance

Vote Majority is greater than 50% Possible Voters: Nodes (1 each) + 1 Witness (Disk or File Share) 4 Quorum Types

Replicated Storage from vendor ? Vote

Site B Site A Cross site network connectivity broken! Can I communicate with majority of the nodes in the cluster? Yes, then Stay Up Can I communicate with majority of the nodes in the cluster? Yes, then Stay Up Can I communicate with majority of the nodes in the cluster? No, drop out of Cluster Membership Can I communicate with majority of the nodes in the cluster? No, drop out of Cluster Membership 5 Node Cluster: Majority = 3 Majority in Primary Site Node Majority

Site BSite A Disaster at Site 1 We are down! Can I communicate with majority of the nodes in the cluster? No, drop out of Cluster Membership Can I communicate with majority of the nodes in the cluster? No, drop out of Cluster Membership Majority in Primary Site 5 Node Cluster: Majority = 3 Need to force quorum manually

Site ASite B Site C Complete resiliency and automatic recovery from the loss of any 1 site Replicated Storage \\Foo\Cluster1 WAN Multi-Site With File Share Witness File Share Witness

WAN Site A Site B Site C Complete resiliency and automatic recovery from the loss of connection between sites Replicated Storage Multi-Site With File Share Witness Can I communicate with majority of the nodes (+FSW) in the cluster? Yes, then Stay Up Can I communicate with majority of the nodes (+FSW) in the cluster? Yes, then Stay Up File Share Witness Can I communicate with majority of the nodes in the cluster? No (lock failed), drop out of Cluster Membership Can I communicate with majority of the nodes in the cluster? No (lock failed), drop out of Cluster Membership \\Foo\Cluster1

AreaConsiderations Network-On cross-subnet failover, if guest is … -DHCP, then IP updated automatically -Statically configured IP, then admin needs to configure new IP -Use VLAN preferred with live migration between sites Storage-3 rd party replication solution required -Configuration with CSV (explained next) Quorum-No special considerations Links:

VHD Nodes in Primary Site Nodes in Disaster Recovery Site Read/OnlyRead/Write Replication VM attempts to access replica

AreaConsiderations Network-SQL does not support OR dependency -Need to stretch VLAN between sites Storage-No special considerations -3 rd party replication solution required Quorum-No special considerations Links:

AreaConsiderations Network-No VLAN needed -Change HostRecordTTL from 20 minutes to 5 minutes -CCR supports 2 nodes, one per site Storage-Exchange CCR provides application- based replication Quorum-File share witness on the Hub Transport server on primary site Links:

HVNODE1 (Microsoft Hyper-V Server 2008 R2) HVNODE2 (Windows Server 2008 R2 deployed as Server core)

Cluster Team Blog: Cluster Information Portal: Clustering Technical Resources: resources.aspxhttp:// resources.aspx Clustering Forum (2008): Clustering Forum (2008 R2): US/windowsserver2008r2highavailability/threads/ US/windowsserver2008r2highavailability/threads/ Clustering Newsgroup: us/default.aspx?dg=microsoft.public.windows.server.clusteringhttp:// us/default.aspx?dg=microsoft.public.windows.server.clustering Failover Clustering Deployment Guide: TechNet: Configure a Service or Application for High Availability: TechNet: Installing a Failover Cluster: TechNet: Creating a Failover Cluster: Webcast (2008 R2): Introduction to Failover Clustering: Webcast (2008 R2): HA Basics with Hyper-V: Webcast (2008 R2): Cluster Shared Volumes (CSV):

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