Exchange Server 2010 High Availability Deep Dive

2. UCC402 Exchange Server 2010High Availability Deep Dive Scott Schnoll Principal Technical Writer Microsoft Corporation

3. Agenda • Exchange Server 2010 High Availability Deep Dive • Database Availability Group Networks • Active Manager • Best Copy Selection • Datacenter Activation Coordination Mode

4. Exchange Server 2010 High Availability Deep Dive: Database Availability Group Networks

5. DAG Networks • A DAG network is a logical collection of one or more subnets • There are two types of DAG networks • MAPI Network - connects DAG members to network resources (Active Directory, other Exchange servers, DNS, etc.) • Registered in DNS / DNS configured • Uses default gateway • Client for Microsoft Networks/File and Print Sharing enabled • Replication Network - used for/by continuous replication (log shipping and seeding) • Not registered in DNS / DNS not configured • No default gateway • Client for Microsoft Networks/File and Print Sharing disabled

6. DAG Networks • All DAGs must have: • Exactly one MAPI network • Zero or more Replication networks • Separate network(s) on separate subnet(s) • LRU determines which replication network is used with multiple replication networks • DAG networks automatically created when Mailbox server is added to DAG • Based on cluster’s enumeration of networks, which uses subnets • One cluster network is created per subnet

7. DAG Networks • Maximum round trip return latency between all DAG members must be 500 ms or less • Regardless of network latency, validate that the network between all DAG members is capable of satisfying your data protection and availability goals • May need to increase the number of databases or decreasing the number of mailboxes per database to achieve goals

8. DAG Networks

9. DAG Networks

10. DAG Networks • Collapse DAG networks and disable replication on MAPI network: Set-DatabaseAvailabilityGroupNetwork -Identity DAG2\DAGNetwork01 -Subnets 192.168.0.0,192.168.1.0 -ReplicationEnabled:$false Set-DatabaseAvailabilityGroupNetwork -Identity DAG2\DAGNetwork02 -Subnets 10.0.0.0,10.0.1.0 Remove-DatabaseAvailabilityGroupNetwork -Identity DAG2\DAGNetwork03 Remove-DatabaseAvailabilityGroupNetwork -Identity DAG2\DAGNetwork04

11. DAG Networks • Collapse DAG networks and disable replication on MAPI network: Set-DatabaseAvailabilityGroupNetwork -Identity DAG2\DAGNetwork01 -Subnets 192.168.0.0,192.168.1.0 -ReplicationEnabled:$false Set-DatabaseAvailabilityGroupNetwork -Identity DAG2\DAGNetwork02 -Subnets 10.0.0.0,10.0.1.0 Remove-DatabaseAvailabilityGroupNetwork -Identity DAG2\DAGNetwork03 Remove-DatabaseAvailabilityGroupNetwork -Identity DAG2\DAGNetwork04

12. DAG Networks • All DAGs extended to multiple datacenters should have hotfix from KB 2550886 installed • Automatic detection occurs when members added to DAG • If NICs are added after server is member of DAG, you must perform discovery • Set-DatabaseAvailabilityGroup<DAGName> -DiscoverNetworks • DAG network configuration persisted in cluster database • HKLM\Cluster\Exchange\DAG Network • DAGs include built-in encryption and compression • Encryption: Kerberos SSP EncryptMessage/DecryptMessage APIs • Compression: Microsoft XPRESS, based on LZ77 algorithm

13. DAG Networks • When using a single NIC • It is both the MAPI and the Replication network • EnableReplication is $True • When using multiple NICs • One NIC is the MAPI network • EnableReplication is $False • Other NIC(s) are Replication network(s) • Replication uses LRU to pick Replication network to use • If Replication networks are unavailable, MAPI network is used

14. DAG Networks • Use netsh, router ACLs or other means to block cross-network traffic Allowed M M M M Subnet 1 Subnet 3 R R R R Subnet 2 Subnet 4 Blocked

15. DAG Networks • If using iSCSI storage, configure DAG and cluster to ignore iSCSI networks • Set-DatabaseAvailabilityGroupNetwork-Identity <DAGNetworkName> -ReplicationEnabled:$false -IgnoreNetwork:$true

16. DAG Networks • When a DAG spans multiple subnets you need an IP address on the MAPI network for each subnet • Use DHCP in site resilience configurations to assign IP addresses to Replication network • Enables delivery of the typically required static routes • If using static IP addresses, use netsh to configure static routes • Configure a DNS TTL on namespace records consistent with your SLA • For example, use a TTL of 5 minutes for a 60 minute RTO SLA

17. Exchange Server 2010 High Availability Deep Dive: Active Manager

18. Active Manager • What are the three Active Manager roles? • Standalone • PAM (Primary Active Manager) • SAM (Standby Active Manager) • Transition of role state logged into Microsoft-Exchange-HighAvailability/Operational event log (Crimson Channel)

19. Active Manager Functionality • Mount and Dismount Databases • Provide Database Availability Information • Provide Interface for Administrative Tasks • Monitor for and React to Failures • Maintains Database and Server State Information

20. Mount / Dismount Database Copy • Mount Database • An administrator action invoked through a task • The last part of a move operation • Dismount Database • An administrator action invoked through a task • The first part of a move operation

21. Auto Dismount – DAG Member • Occurs when a DAG loses quorum • All DAG members are running (but may not be participating in the cluster) • Databases dismounted as quickly as possible to avoid split-brain • Information Store service is terminated

22. Active Manager – Move Database • Move Database • An administrator action invoked by a task • Automatic operation initiated by the PAM (failover) • Begins with a Dismount operation and ends with a Mount operation

23. Exchange Server 2010 High Availability Deep Dive: Best Copy Selection

24. Best Copy Selection • Active Manager selects the “best” copy to become the new active copy when the existing active copy fails, or when an administrator performs a target-less switchover • BCS is the process of finding the best copy of an individual database to activate, given a list potential copies for activation and their status • During BCS, any servers that are unreachable or activation blocked are ignored

25. Best Copy Selection – RTM • Sorts copies by copy queue length to minimize data loss, using activation preference as a secondary sorting key if necessary • Selects from sorted listed based on which set of criteria met by each copy • Attempt Copy Last Logs (ACLL) runs and attempts to copy missing log files from previous active copy

26. Best Copy Selection – SP1 • Sorts copies by activation preference when auto database mount dial is set to Lossless • Otherwise, sorts copies based on copy queue length, with activation preference used a secondary sorting key if necessary • Selects from sorted listed based on which set of criteria met by each copy • Attempt Copy Last Logs (ACLL) runs and attempts to copy missing log files from previous active copy

27. Best Copy Selection • Is database mountable? • Is copy queue length <= AutoDatabaseMountDial? • If Yes, database is marked as current active and mount request is issued • If not, next best database tried (if one is available)

28. Best Copy Selection

29. Best Copy Selection – RTM • Four copies of DB1 • DB1 currently active on Server1 Server1 Server2 Server3 Server4 X DB1 DB1 DB1 DB1

30. Best Copy Selection – RTM • Sort list of available copies based by Copy Queue Length (using Activation Preference as secondary sort key if necessary): • Server3\DB1 • Server2\DB1 • Server4\DB1

31. Best Copy Selection – RTM • Only two copies meet first set of criteria for activation (CQL< 10; RQL< 50; CI=Healthy): • Server3\DB1 • Server2\DB1 • Server4\DB1 Lowest copy queue length – tried first

32. Best Copy Selection – SP1 • Four copies of DB1 • DB1 currently active on Server1 • Auto database mountdial set to Lossless Server1 Server2 Server3 Server4 X DB1 DB1 DB1 DB1

33. Best Copy Selection – SP1 • Sort list of available copies based by Activation Preference: • Server2\DB1 • Server3\DB1 • Server4\DB1

34. Best Copy Selection – SP1 • Sort list of available copies based by Activation Preference: • Server2\DB1 • Server3\DB1 • Server4\DB1 Lowest preference value – tried first

35. Best Copy Selection • After Active Manager determines the best copy to activate • The Replication service on the target server tries to copy missing log files from source (ACLL) • If successful, database will mount with zero data loss • If unsuccessful (lossy failure), database will mount based on the AutoDatabaseMountDial setting • If data loss is outside of dial setting, next copy will be tried

36. Best Copy Selection • If an activated database copy is mounted • It will generate new log files (using the same log generation sequence) • Transport Dumpster requests will be initiated for the mounted database to recover lost messages • When original server or database recovers, it will run through divergence detection and either perform an incremental resync or require a full reseed

37. Exchange Server 2010 High Availability Deep Dive: Datacenter Activation Coordination Mode

38. Datacenter Activation Coordination Mode • DAC mode is a property of a DAG • Acts as an application-level form of quorum • Controls whether or not a Mailbox server attempts to automatically mount its active databases on startup • Designed to prevent multiple copies of same database mounting on different members due to loss of network (split brain) • Also enables use of Site Resilience tasks • Stop-DatabaseAvailabilityGroup • Restore-DatabaseAvailabilityGroup • Start-DatabaseAvailabilityGroup

39. Datacenter Activation Coordination Mode • RTM: DAC Mode for DAGs with three or more members that are extended to two Active Directory sites • Don’t enable for two-member DAGs where each member is in different AD site or DAGs where all members are in the same AD site • SP1: DAC Mode can be enabled for all DAGs • If using Third Party Replication (TPR) mode, check with your vendor for guidance on DAC mode

40. Datacenter Activation Coordination Mode • Uses Datacenter Activation Coordination Protocol (DACP) • A bit in memory (in MSExchangeRepl.exe) set to either: • 0 = can’t auto-mount at startup • 1 = can auto-mount at startup

41. Datacenter Activation Coordination Mode • Active Manager startup sequence • DACP is set to 0 • DAG member communicates with other DAG members it can reach to determine the current value for their DACP bits • If the starting DAG member can communicate with all other members on the StartedMailboxServers list, DACP bit switches to 1 • If the starting DAG member can communicate with another member, and that other member’s DACP bit is set to 1, starting DAG member DACP bit switches to 1 • If the starting DAG member can communicate with another member, and that other member’s DACP bits are set to 0, starting DAG member DACP bit remains at 0

42. Datacenter Activation Coordination Mode

43. Datacenter Activation Coordination Mode

44. Datacenter Activation Coordination Mode 0 0 1 1

45. Related Content • UCC305 - Exchange Server 2010 High Availability Design

46. Resources • Exchange Team Blog • http://aka.ms/EHLO • Exchange 2010 Documentation Library • http://aka.ms/Ex2010Docs

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48. Questions? • UCC402 • Scott Schnoll • Principal Technical Writer • scott.schnoll@microsoft.com • http://blogs.technet.com/scottschnoll • Twitter: @schnoll • You can ask me questions at the “Ask the Expert” zone: • November 10, 2011 12:30 – 13:30