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Attention, Session en Anglais. Attention Session en 2 parties. Ceci est la première partie. Cette session sera animée par Scott Schnoll, Senior Content Developer chez Microsoft Corp et veritable Gourou Exchange. La messagerie est un élément ultra critique du système d'information : Elle ne DOIT PAS tomber. Pour cela, Exchange 2013 intègre les toutes dernières technologies en terme de tolérance de panne et de haute disponibilité. Scott Schnoll vous expliquera la mécanique de l'intérieur ! Cette session vous donne accès à l'état de l'art sur Exchange. C'est LA session à suivre pour découvrir la mécanique de haute disponibilité d'Exchange 2013. Speaker : Scott Schnoll (Microsoft)
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Infrastructure, communication & collaboration
Exchange Server 2013
High Availability and Site Resilience (1/2)
Scott SchnollSenior Content Developer
Microsoft Corporation
scott.schnoll@microsoft.comhttp://aka.ms/Schnoll
Twitter: @Schnoll
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• Database Availability Group Internals• Witness Server
Agenda – Part 1
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• Dynamic quorum• DAG member maintenance
Agenda – Part 2 (16:30-17:15, salle 253)
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DATABASE AVAILABILITY GROUP INTERNALS
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• Microsoft Exchange Replication service
• Active Manager Client component• Microsoft DAG Management service• Cluster service and components• Windows Crimson Channel
DAG Internals
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• Introduced in Exchange 2007 RTM– Microsoft Exchange Replication service |
MSExchangeRepl– MSExchangeRepl.exe– Required on all Mailbox servers (not just DAG
members)– Communicates with Active Directory and other
DAG members
DAG Replication Service
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• Active Directory lookup• Copy status lookup• Replay core manager• Seed manager• Autoreseed manager• Disk reclaimer manager• Replay RPC server
wrapper• Remote data provider
wrapper
• Active Manager• Active Manager RPC
server wrapper• Failure item manager• TPR API manager• Support API manager• Server locator manager• Health state tracker• VSS Writer
DAG Replication Service• Includes 16 components
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• Runs inside client access and transport services– Microsoft Exchange RPC Client Access -
MSExchangeRPC– Microsoft Exchange Transport –
MSExchangeTransport– Microsoft Exchange Frontend Transport –
MSExchangeFrontendTransport– Client Access Front End (CAFÉ) components
Active Manager Client Component
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• When connecting clients or routing messages, client access and transport services query Active Directory and Active Manager to find out location of the active copy of a mailbox– DAG members with Standby Active Manager
(SAM) role respond to these queries
Active Manager Client Component
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• Introduced in Exchange 2013 CU2– Microsoft Exchange DAG Management service | MSExchangeDagMgmt
– MSExchangeDagMgmt.exe– Runs on all Mailbox servers (not just DAG members)– Communicates with Active Directory and other DAG
members
• Includes 4 components– Active Directory lookup– Copy status lookup– Monitoring– Tracer instance
DAG Management Service
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• Created for two primary reasons:– so the Replication service can have more focused
functionality– so Managed Availability actions can kill lower-priority
activities
• Logs events in same place as Replication service
• Other functions will move to this service– AutoReseed, Disk reclaimer, Dynamic replay lag playdown– Future AutoDAG copy layout and mobility features
DAG Management Service
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• Introduced in NT Server Enterprise Edition (1997)– Cluster Service | ClusSvc– Clussvc.exe
• Exchange DAGs use several cluster components– Membership and node management– Networks and heartbeating– Quorum– Cluster registry
Cluster service
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• Quorum is required in order to mount databases• Quorum is based on votes, not membership• Voting can be rigged
– Votes can be taken away manually or dynamically
• Exchange manages quorum model, not quorum– Exchange management of quorum model based on nodes, not
votes– Removing votes requires manual configuration of quorum
model– Exchange will make incorrect quorum model management
decisions if votes are manually removed at the cluster level
Cluster service
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• Active Manager stores database / server information in the cluster registry for DAG members– Registry changes are replicated immediately to all DAG
members
• Stored information is used as part of BCSS
Cluster registry
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• ActiveServer– Name of server where database is currently mounted
or expected to be mounted when mount operation completes
• LastMountServer– Name of server where database was last successfully
mounted
• LastMountedTime– Date and time stamp of the last time database was
mounted
Cluster registry
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• MountStatus– Current mount status for database (mounted /
dismounted)
• IsAdminDismounted– Designates whether current dismounted status is
the result of administrator action (true / false)
• IsAutomaticActionsAllowed– Designates whether the database can be
automatically activated (true / false)
Cluster registry
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• Applications and Services logs– Area of Windows Server event log used by applications for logging and
internal communication– These logs store events from a single application or component rather
than events that might have system-wide impact– This is referred to as an application's crimson channel
• Exchange 2013 has a crimson channel with multiple areas– ActiveMonitoring– HighAvailability– MailboxDatabaseFailureItems– ManagedAvailability– PushNotifications– Troubleshooters
Crimson Channel
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WITNESS SERVER AND WITNESS SERVER PLACEMENT
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• A server that participates in a failover cluster with an even number of members– Is not a member of the cluster/DAG– Does not contain a copy of quorum data
• File share on this server is represented by File Share Witness resource in cluster core resource group– Uses IsAlive check for availability
Witness Server
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• File Share Witness Resource Behavior– If server or share are not available, cluster resources are
failed and moved to another node– If FSW resource does not come back online, it remains in
a Failed state, with restart attempts every 60 minutes– If witness server needed for quorum, and resource
cannot be brought online, quorum will be lost• Single restart attempt for FSW resource in Failed state• No restart attempt for FSW resource in Offline state
Witness Server
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• When witness server is needed to maintain quorum, one of the nodes locks the witness.log on witness server– Node that locks witness.log file is called the locking
node– If enough nodes are in contact with the locking
node to constitute a majority, quorum is maintained– Nodes that can’t communicate with locking node
lose quorum
Witness Server
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• Attempts to lock witness.log file occur in a specific order– Node that owns cluster core resource group
tries immediately– Nodes not owning cluster core resources wait 6
seconds before trying
Witness Server
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Witness Server• Cluster Core Resources• Sequence #: 20
• Sequence #: 20
Cluster state change – node owning cluster core resources locks FSW – updates sequence number
• Cluster Core Resources• Sequence #: 21
• Lock witness.log• Sequence #: 21
Challenging node attempts witness lock. Lock already exists – sequence # higher, challenge not successful.
All nodes available. FSW lock released. Changes replicated, sequence numbers in sync.
• Sequence #: 22
• Cluster Core Resources• Sequence #: 22
0 1 5432 6 7 111098 12 13 161514
#mstechdays Infrastructure, communication & collaboration
Witness Server• Cluster Core Resources• Sequence #: 20
Cluster state change – node owning cluster core resources unavailable.
• Cluster Core Resources• Sequence #: 21
• Lock witness.log• Sequence #: 21
Challenging node attempts witness lock. No lock exists, lock successful, sequence number updated.
All nodes available. FSW lock released. Changes replicated, sequence numbers in sync.
• Sequence #: 22
• Cluster Core Resources• Sequence #: 22• Sequence #: 20
0 1 5432 6 7 111098 12 13 161514
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• Exchange 2010 guidance– “We recommend that you use a Hub Transport server
running on Exchange Server 2010 in the Active Directory site containing the DAG. This allows the witness server/directory to remain under the control and visibility of an Exchange administrator.”
– “If your DAG is extended to multiple datacenters, we recommend deploying the witness server in the datacenter considered to be the primary datacenter.”
Witness Server Placement
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• Exchange 2013 guidance more complicated due to options introduced by architectural changes
• Exchange 2013 includes support for new DAG configuration options– A third location, such as a third physical datacenter or
branch office
• Ultimately, the placement of a DAG’s witness server depends on your business requirements and the options available to you
Witness Server Placement
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Witness Server PlacementDeployment scenario Placement RecommendationSingle DAG deployed in one datacenter
Locate witness server in the same datacenter as DAG members
Single DAG deployed across two datacenters; no additional locations available
Locate witness server in primary datacenter
Multiple DAGs deployed in one datacenter
Locate witness server in the same datacenter as DAG members. Additional options include:• Using the same witness server for multiple DAGs• Using a DAG member to act as a witness server for a
different DAG
Multiple DAGs deployed across two datacenters
Locate witness server in the same datacenter as DAG members. Additional options include:• Using the same witness server for multiple DAGs• Using a DAG member to act as a witness server for a
different DAG
Single or Multiple DAGs deployed across more than two datacenters
Locate the witness server in the datacenter where you want the majority of quorum votes to exist
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• If your organization has a 3rd location, a witness server can be deployed there for automatic database failover between two other sites– The witness server location must have network
infrastructure and connectivity that is isolated from network failures that affect the two datacenters with DAG members
• For all DAGs, the availability of the witness server should be on the Exchange administrator’s radar
Witness Server Placement
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• IaaS providers and cloud providers are not supported for use as a witness server– This includes Windows Azure, which does not
yet support the required underlying network configuration to allow an Azure file server VM to act as a witness server in a multi-datacenter deployment
– More info at http://aka.ms/DAGAzure
Witness Server Placement
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• Exchange 2013 Haute disponibilité et tolérance aux sinistres (Session 2/2 première partie) – 12/02/14 - 16:30-17:15, salle 253
• Exchange 2013 Dimensionnement et Performance – 12/02/14 – 17:45-18:30, salle 252B
Related Content
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QUESTIONS?
Thank You!
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