The document discusses SQL Server AlwaysOn technologies, focusing on high availability solutions including AlwaysOn Availability Groups and AlwaysOn Failover Cluster Instances. It outlines the architecture, benefits, and complexities of each solution while emphasizing the foundational role of Windows Server Failover Clustering. The presentation also touches on installation, configuration, and operational considerations for managing these technologies effectively.

1. SQL Server
AlwaysOn for
Dummies
Mark Broadbent
Principal SQL Consultant
SQLCloud
SQLCLOUD.CO.UK

2. About
Mark Broadbent
“Possibly the hardest drinking DBA on the planet”
“30 billion times more intelligent than a live mattress”
Email: mark.broadbent@sqlcambs.org.uk
Twitter: retracement
Blog: http://tenbulls.co.uk
PASS UK Regional Mentor
Event Lead to the UK’s first ever SQLSaturday (Cambridge)
Event #2nd due on Friday 27th Sept 2013 (pre-con) 28th Sept (Community day)
http://www.sqlsaturday.com/228/eventhome.aspx
Cambridgeshire PASS Chapter UG Leader http://sqlcambs.org.uk

3. SQLSaturday Cambridge 2013
27th (pre-con) and 28th (free) September
http://www.sqlsaturday.com/228
Queen’s College, Cambridge CB3 9ET
What is the air-speed velocity of an unladen swallow?

4. Agenda
Windows Server
Failover Clustering
& Quorum
AlwaysOn
Availability Groups
AlwaysOn Failover
Clustered Instances
Introduction to
AlwaysOn
3
2
1
4

5. Introduction to AlwaysOn

6. AlwaysOn Technologies*1
*1 According to my interpretation!
AlwaysOn
Availability Groups
AlwaysOn Failover
Clustered Instances
Database
Mirroring
Scalable Shared
Database
Replication

7. “AlwAys On” isnae new!

8. Dr. Evil
Senior Microsoft
Windows Clustering
Program Manager

9. Don’t let the terms confuse you!
Cluster Node
Cluster Server
Node
Server
Cluster Group
Role
Service or Application
Virtual Server
Failover Cluster
Clustered Instance
SQL Server
Server
Resources (take your pick)
Quorum
Client Network
Private Network
Interconnect
Internal Network
Public Network...
LAN
SAN
Shared Storage
Disk
Cluster Storage
Active/Passive
Single Instance
Multi Instance
N+n Cluster
Majority
Votes
Availability Group
Replica
Readonly Replica

10. AlwaysOn Clustered Instances Provide…
• Abstraction of SQL instance
• High availability of Instance name
• Instance and related services failover as a unit
• Instance components such as jobs and logins not
a consideration
• Distributed Transaction Support
BUT
• Shared data with single point of failure per
instance.
• Complex to administrate

11. Availability Groups Provide…
• Abstraction at the databases level
• Failover as a single Unit
• High availability of “Instance” (listener) name
• All the benefits of DB Mirroring
….and less of the problems (FS is supported)
BUT
• Connected replicas are potentially single point of failure (i.e
user error – deletion of records)
• Complex (arguably less than FCI) to administrate
• Instance level components not failed over –contained dbs
partially come to the rescue
• No Distributed Transaction support for failover

12. AlwaysOn is…

13. Windows Server
Failover Clustering
The foundation of AlwaysOn

14. “The Magic” of Clustering
Clustered
“Application”
Cluster Nodes
The “magic” of clustering is the ability for the cluster to ensure only one set of services,
executables and resources are alive on one node for a clustered application at any one time.
A clustered application will be installed onto each node

15. “The Magic” of Clustering
Clustered
“Application”
Cluster Nodes
failover

16. “The Magic” of Clustering
Clustered
“Application”
Cluster Nodes
failover

17. Storage
Network
Internal
Network
A Basic Windows Cluster
Public
(or Client) Network
Shared
(or Asymmetric) Storage
Quorum
The Cluster
Group
Cluster Node
Cluster Service

18. Understanding Quorum
I’m
Alive!

19. Quorum Models
Node majority (no witness)
Node majority with witness (disk or file share)
No majority (disk witness only)
+Node weighting
Dynamic weighting -new to
Windows 2012

20. DEMO
Taking a look at our Cluster

21. AlwaysOn Failover
Clustered Instances
Instance Level High Availability

22. Installation
Create and install your clustered
instance on the first cluster node
For all other nodes install
executables on every other node

23. Clustered Instances
Node A Node B
SQL Server Instance A
Role (formerly known as
Cluster Group)
Network
Name

24. Clustered Instances
failoverNode A Node B
SQL Server Instance A
Role (formerly known as
Cluster Group)
Network
Name

25. AlwaysOn
Availability Groups
Database[s] Level High Availability

26. Availability Group consists of…
Listener
(Name and
IP)
Availability
Group
Resource
Availability
Group
Databases
SQL Instance Components Wndows Cluster Resources
Replica/s
Availability
Cluster Group
Mirroring
Endpoints
Availability
Group
Listener
(Name and
IP)
Do not flippin’ touch!

27. Transaction Logs
Secondary Replica
SQL Server Instance A
Transaction Logs
Primary Replica
SQL Server Instance A
Availability Groups
Transaction Logs
Redo
Sync/ Async
Secondary Replica
SQL Server Instance B
Listener

28. Transaction Logs
Secondary Replica
SQL Server Instance A
Availability Groups
Transaction Logs
Sync/ Async
Secondary Replica
SQL Server Instance B
Listener
Redo
Transaction Logs
Primary Replica
SQL Server Instance B

29. Availability Groups and Readable Secondaries
• 5 Replicas
• 2 Synchronous, others Asynchronous
• 1 Read-Write
• 4 either Read-only, Read-Intent or No Access

30. DEMO
Using AlwaysOn

31. ReadOnly Routing
• Set connection string property
ApplicationIntent=ReadOnly
• Must connect to a listener.
• Modify Secondary Replica Roles with read
only routing url.
• Modify Primary Replica Roles with read only
routing list.

32. In Summary…
• It is not all Butterflys and Unicorns so choose the
HA solution appropriate to your requirements.
• Failover Clustering is a very mature technology
but requires specialist skill and understanding. It
does not provide scalability.
• Availability Groups partially rely on Windows
Clustering but are slightly easier to setup and
manage. They also provide reporting query
scalability.

33. Tha mo bhàta-foluaimein loma-làn easgannan
for attending this session and
SQLSaturday #202 in Edinburgh
Thank you!