Windows Server 2012 Failover Cluster Disaster RecoveryAlex PubanzSenior Premier Field EngineerMicrosoft Australia

MDC-B355

Agenda

• Cluster Definition and Benefits• Multi-Site Cluster• The Paxos Tag• Restoring a failover cluster from

backup• Cluster Name Object (CNO)

Recovery• Replacing a shared disk• Quorum Recovery

Cluster Definition and Benefits

Cluster Definition and Benefits• A cluster is a group of independent servers

that function as a single system• Clusters are managed as a single unit• Benefits:

• High Availability• Scalability• Reduced Total Cost of Ownership

Failover Cluster Workloads include:• Hyper-V• File/Print • SQL• Exchange• and more

Multi-Site Cluster

Benefits of a Multi-Site Cluster

• Protects against loss of an entire location

• Automates failover• Reduced downtime• Lower complexity disaster recovery plan

Site BSite A

SANSAN

But what about deleted or corrupted cluster configuration in the clusdb or Active Directory?

The Paxos Tag

The Paxos Tag

• Consists of 3 numbers separated by a colon

• Stored in HKLM\Cluster• Provides the guarantee of

consistency across the cluster nodes and witness disk

• Used to guarantee data consistency when updates are propagated.

• Can be used to verify if an authoritative restore of the clusdb occurred

The Paxos Tag – What makes it update?• Paxos Tag changes during the following

conditions:• Epoch - Every time a cluster is formed• Sequence - Every time there is an update to the

configuration of the cluster

• Sync process sends out proposal to all nodes in the cluster• Consists of Proposal Number and Sequence Number.• Nodes check local config (registry) to see if sequence

is higher or lower than current proposal• If the node has a lower number then the proposal the

Node sends out acceptance of the proposal• If a majority of the nodes in the cluster (a consensus)

send back acceptance the data is incorporated locally.

The Paxos Tag – What makes it change?• Format can change in the following two

scenarios• Authoritative Restore of the cluster is executed• When the cluster is started using the /forcequorum

switch (/FQ)

date/time format example after an authoritative restore:2013/05/27-15`35`55.889_4:2013/05/27-15`35`55.889_4:294

Restoring a failover cluster from backup

Auth- vs. Non-Authoritative Restore

Non-Authoritative RestoreRestores the node to normal function, but is not rolling back the cluster configuration• used when a damaged cluster node needs to be restored to normal function

Authoritative RestoreRestores the cluster configuration to the configuration stored in the backup• used when deleted or corrupt cluster configuration needs to be

restored

DEMO

BMR restore after a full cluster meltdown using Windows RE and System Center DPM 2012 SP1

DEMO

Authoritative Restore using Windows Server Backup

Cluster Name Object (CNO) Recovery

Cluster Name Object (CNO) Recovery• CNO is the ‘common identity’

for a Failover Cluster and stored in AD

• The CNO creates all other Network Name resources that are created in a Failover Cluster as part of a Client Access Point (CAP)

• The CNO is responsible for synchronizing the domain password for each Virtual Computer Object (VCO) it created

Demo

Recovering a deleted Cluster Name Object (CNO) and Virtual Computer Objects (VCO) in Active Directory

Replacing a shared disk

Replacing a Shared Disk• Enable Disk Maintenance Mode on (failed) disk to suspend all

Basic\Thorough health checks and all Persistent Reservation processes

• Attach a new disk• Online and initialize the disk is disk management (MBR or

GPT)• Create a new volume • Format as either FAT32, NTFS or ReFS (depending on

requirements)• Right-click the disk resource in Failover Cluster Manager,

‘More actions…’, ‘Repair’. This will launch the ‘Repair a Disk Resource’ window.• Bring the new resource online• Copy/restore data to the new drive

Demo

Failover Cluster Manager’s built in ‘repair’ disk functionality

Quorum Recovery

The Four Quorum Models• Default model when you create a cluster without storage

• Recommended model when your cluster has an odd number of nodes

Node Majority• Default model when you create a cluster with

storage (and at least one disk with an NTFS file system)

• \Cluster folder will be created which contains a complete copy of the cluster registry HIVE HKLM\Cluster

• Recommended when you have an even number of nodes

Node and Disk Majority

• Needs to be configured manually• Connection to a SMB network share required• FSW contains log file with Paxos tag information

Node and File Share Majority

• Manual configuration required• Single point of failure• Useful when the majority of cluster nodes is not

available (hardware failure?)

No MajorityDisk Only

Demo

Recovering a failed file share witness quorum resource

AppendixMicrosoft Premier Proactive ServicesCSRES – Cluster Server Recovery Execution Service (ask your TAM about it!)http://download.microsoft.com/documents/australia/services/datasheets2012/Cluster Service Recovery Execution Service (CSRES).pdf

Understanding Backup and Recovery Basics for a Failover Clusterhttp://technet.microsoft.com/en-us/library/cc771973.aspx

Recovering a Deleted Cluster Name Object (CNO) in a Windows Server 2008 Failover Clusterhttp://blogs.technet.com/b/askcore/archive/2009/04/27/recovering-a-deleted-cluster-name-object-cno-in-a-windows-server-2008-failover-cluster.aspx

SC 2012 SP1 – DPM: Leveraging DPM ScaleOut feature to protect VMs deployed on a big clusterhttp://blogs.technet.com/b/dpm/archive/2013/05/01/sc-2012-sp1-dpm-leveraging-dpm-scaleout-feature-to-protect-vms-deployed-on-a-big-cluster.aspx

Related contentMDC-B337 Failover Cluster Networking EssentialsMDC-B336 Cluster in a Box in 2013: How Real Customers Are Making Their Businesses Highly-Available with Windows Server 2012Find Me Later At...

Track resourcesLearn more about Windows Server 2012 R2 Preview, download the datasheet and evaluation bits on http://aka.ms/WS2012R2Learn more about System Center 2012 R2 Preview, download the datasheet and evaluation bits on http://aka.ms/SC2012R2

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