2. High Availability - SQL Cluster
This session is intended to give an overview of Failover Clustering with regards to SQL Server
- Presentation Title shouldn’t take more than 30 sec.

3. About Me Tonatiuh Islas SQL DBA Analyst at Flex. Trajectory Contact
SQL DBA Advisor at Dell Services Mexico.
SQL DBA at Ryder Mexico.
Primary SQL DBA at Bank of America.
Contact
This presentation won’t take more than 2 min.

4. Agenda High Availability (HA) vs Disaster recovery (DR)
SQL Server’s High Availability Technologies
Introduction to Windows failover cluster
Components on SQL and Windows Failover Cluster (Quorum models, networks for clustering and basic storage configuration)
SQL Clustering Architecture
Differences between WSFC and FCI
Installing SQL Server on a Windows cluster
Administering SQL Server on a cluster
Demo
Q&A
This slide won’t take more than 1 minute
REMEMBER: Questions and Answers at the end of the presentation.

5. High Availability.- Definition and nines of availability
Availability is traditionally measured according the percentage of time that the system is available to its end users.
Refers to solutions that are more local in nature and generally tolerate smaller amounts of data loss and downtime.
Percentage of availability = ((total elapsed time – sum of downtime)/total elapsed time). “Nines of availability”
Percentage Availability
Dowtime per year
Downtime per Month
Downtime per Week
99.0%
3.65 Days
7.30 hrs
1.68 hrs
99.9%
8.76 hrs
43.8 mins
10.1 mins
99.99%
52.6 mins
4.38 mins
1.01 mins
99.999%
5.26 mins
26.28 secs
6.06 sec
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6. High Availability.- Factors Influencing Availability
Personnel Factors. Human error stems from two main sources: administrative errors and end user errors. Fixed hiring the best and most qualified personnel getting a regular training routine.
Operational Factors. Inefficient internal processes. Fixed establishing efficient and standardized operational procedures can eliminate unnecessary downtime. Documentation and standardized hardware along with software configurations.
Technical Factors. Unplanned downtime and planned downtime. Unplanned downtime is further complicated by many factors like SLAs and disaster recovery plans.
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7. Disaster Recovery.
A disaster is an event that causes data loss or any serious business disruption.
Causes of a disaster can be numerous: power failure, hardware failure, virus attack, natural disaster, human error, etc.
Disaster recovery plan types include the following:
A communication plan.
Instructions for contacting the people involved in the response to the disaster.
Information about who owns the administration of the plan.
A checklist of required tasks for each recovery scenario
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8. High Availability VS Disaster recovery.
HA is the measurement of a system’s ability to remain accessible in the event of a system component failure.
DR is the process by which a system is restored to a previous acceptable state, after a natural or man-made disaster.
A notable difference is that with HA there is, generally, no loss of service (implemented by building in multiple levels of fault tolerance).
HA uses SLAs (expected for your business and DR uses RTO (Recovery Time Objective) and RPO (Recovery Point Objective).
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9. SQL Server’s High Availability Technologies.
Windows Failover Clustering. Windows failover clustering provides server-level protection from both unplanned and planned downtime.
SQL uses the Windows cluster technology were the main idea is the usage of shared storage and “nodes”
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10. SQL Server’s High Availability Technologies.
Database Mirroring . Database mirroring provides database-level protection from unplanned downtime. Data corruption can be handled in an easy way.
The witness serves as a monitor. It detects if the principal database is not available and tells the mirror database to become the principal in the event that the original principal cannot be contacted
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11. SQL Server’s High Availability Technologies.
Log Shipping . Log shipping is a high-availability and disaster-recovery solution that can be used to protect against unplanned downtime.
Like database mirroring, log shipping works by first restoring a full backup of the primary database to a backup server.
Then transaction log backups are periodically sent from the primary server’s database and applied to the database on the backup server.
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12. SQL Server’s High Availability Technologies.
Peer-to-Peer Replication . Peer-to-peer transactional replication is another data replication technology that can be used to protect against unplanned downtime.
Peer-to-peer transactional replication is designed for bidirectional replication and high availability scenarios.
One advantage to using replication is that the peer servers are continually available.
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13. SQL Server’s High Availability Technologies.
Database Snapshots. Database snapshots allow you to quickly restore a database to a previous point in time.
Database snapshots create copies (or “snapshots”) of a database without the overhead of performing a physical copy of the entire database.
The database snapshot makes a copy of the original database schema.
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14. SQL Server’s High Availability Technologies.
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15. Windows failover cluster.
A failover cluster solution must meet the following hardware requirements:
Storage must be attached to the nodes in the cluster, if the solution is using shared storage.
Device controllers or appropriate adapters for the storage can be Serial Attached SCSI (SAS), Fibre Channel, Fibre Channel over Ethernet (FcoE), or iSCSI.
The complete cluster configuration (servers, network, and storage) must pass all tests in the Validate a Configuration Wizard.
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16. Windows failover cluster.
Cluster service. The essential software component that controls all aspects of server cluster or failover cluster operations. Each node in a failover cluster or server cluster runs one instance of the Cluster service.
LAN Switch
NIC Teaming
The DLL contains the resource-specific code that is necessary to provide high availability for one or more resource types. Each resource type exposes two types of health detection checks
LooksAlive is a lightweight, more frequent check.
IsAlive is run less frequently to do a deeper check that the service is available
Nic
Nic
non routable ip addresses
heartbeat
Switch
Switch
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Storage
Ports

17. Windows failover cluster.
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18. Windows failover cluster.
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19. Windows failover cluster. Network
Public
Normal LAN connectivity
Heartbeat
Used for Cluster communications between nodes
Storage (iSCSI)
TCP connectivity to iSCSI storage
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20. Windows failover cluster. Network
Nic Teaming is used for load balancing and Failover.
In the past, NIC teaming was handled by the NIC vendor’s driver and management software.
One of the new features in Windows Server 2012 is Microsoft NIC Teaming
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Nic Teaming (Virtual) 1 2 3
NFT. Fault Tolerance
NLB. Load Balance
Nic card

21. Windows failover cluster. Quorum
Why quorum is necessary?
When network problems occur, they can interfere with communication between cluster nodes. A small set of nodes might be able to communicate together across a functioning part of a network but not be able to communicate with a different set of nodes in another part of the network.
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22. Windows failover cluster. Quorum Models
Considerations
ODD/EVEN
Local/Remote
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23. Windows failover cluster. Quorum New in Server 2012/R2
Dynamic Quorum
Introduced in Windows Server 2012
Implements “Last Man Standing”
Dynamically removes voting rights
Dynamic Witness
Introduced in Windows Server 2012 R2
Cluster decides whether to use witness
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24. Windows failover cluster. MSDTC
MSDTC is a component of Windows Server and is leveraged by some SQL Server features and applications to coordinate transactions across multiple servers
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25. Topology and Architecture of a SQL Server Cluster.
SQL Clustering components:
Two or more nodes
Shared Storage
Quorum
CNO (Cluster Name Object) and CLUSTERNAME$ in AD
Cluster IP and Network Name
SQL Virtual Network Name and IP
SQL Clustered Installation
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26. Topology and Architecture of a SQL Server Cluster.
Common SQL Server Failover Deployments:
• Single failover cluster instance two-node cluster.
• Multi-instance cluster: o All nodes with active instances. o n+1 (n instances with one spare node).
• Multi-site failover cluster instance.
• Guest failover cluster.
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27. Topology and Architecture of a SQL Server Cluster.
A SQL Server failover cluster instance that is installed on a Windows Server failover cluster is similar to a stand-alone SQL Server instance that does not use Windows Server failover clustering.
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28. Installing a SQL Server Cluster.
Prerequisites
Enable “Failover Clustering” OS feature
Present Shared Storage to all nodes
Pre-stage cluster objects in AD (if needed)
Ensure NIC’s for all networks are configured
Create a WSFC in Windows Server and .Net framework 3.5 (or above)
Obtain successful cluster validation report
Perform SQL Server Clustered Installation
“Add Node” to all secondary nodes
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29. Installing a SQL Server Cluster.
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30. Installing a SQL Server Cluster.
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31. Installing a SQL Server Cluster.
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32. Installing a SQL Server Cluster.
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33. Installing a SQL Server Cluster.
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34. Installing a SQL Server Cluster.
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38. Installing a SQL Server Cluster.
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39. Installing a SQL Server Cluster.
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40. Installing a SQL Server Cluster.
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41. Installing a SQL Server Cluster.
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42. Installing a SQL Server Cluster.
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43. Installing a SQL Server Cluster.
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44. Installing a SQL Server Cluster.
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45. Administering SQL Server on a cluster.
Use “Failover Cluster Manager”
For failover
Look at cluster resources and dependencies
What happens during failover
Primary node SQL services are stopped
Secondary SQL services start and gain control of shared storage
All system/user DB’s live on shared storage
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46. Administering SQL Server on a cluster.
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47. New Features in SQL Server 2012.
Flexible Failover Policy
Levels 0-5 (Default of 3)
LooksAlive/IsAlive replaced by sp_server_diagnostics
Support for multi-subnet clusters
IP Binding using OR algorithm
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48. New Features in SQL Server 2012.
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49. DEMO SQL Server on a cluster.
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50. Q&A
5 minutes for Questions.