1. Navigating the options for Data Redundancy
Wendy Pastrick
SQL Server MVP
BI Consultant, BlueGranite, Chicago

2. About Wendy
DBA since 2000
Professional Association for SQL Server member and volunteer
Chicago Suburban SSUG Chapter

3. AGENDA Defining High Availability A Brief Overview
Replication
Log Shipping
Mirroring
Clustering
How to Choose Which to Use?
Pros and Cons
Compare and Contrast

4. High Availability Different than Disaster Recovery
Is full failover necessary?
How much downtime is acceptable?
Are personnel available to assist in a failover?
What hardware resources can be utilized?
What is the physical distance between servers?
More options than what is covered in this presentation!

5. Replication Transactional, Peer-to-Peer and Merge options
Publishers and Subscribers
Distribution database
All databases available for use
Most flexibility with replication option
Can be complex and monitoring required

6. Transactional Replication
Push or Pull subscribers

7. Peer-to-Peer

8. Merge Replication Push or Pull Subscribers
Conflict Resolvers as All subscribers can be updated

9. Replication Use Case
Distributed Subscribers
Reporting Needs

10. Log Shipping Transfer and application of Log File Backups
Primary to Secondary
SQL Agent Jobs
Fileshares required
Option to have Secondary database in Standby mode for ReadOnly access

11. Log Shipping Topology

12. Log Shipping Use Case Read Only Scenario Built in Delay
possible security benefit
possible data retrieval

13. Mirroring Transactional Application from Logs Principal to Mirror
Utilizes End Points
Synchronous
Asynchronous
Endpoint: An endpoint is a SQL Server object that enables SQL Server to communicate over the network. It encapsulates a transport protocol and a port number.

14. Mirroring Topology Synchronous vs Asynchronous
Synchronous – wait for commit on Mirror
Asynchronous – faster, but some risk of data loss
Synchronous vs
Asynchronous

15. Mirroring Use Case
Geographically dispersed cluster
Poor man’s cluster

16. Clustering AlwaysOn Availability Groups
Database Level
Windows Server Failover Cluster
Instance Level

17. Availability Groups

18. Failover Clustering

19. Pros Replication Log Shipping Mirroring Multiple database support
All copies are fully functional databases
Log Shipping
Simple setup
Witness for monitoring
Can use Secondary as Read-Only
Mirroring
Automatic, Immediate Failover
Least potential for data loss (in Synchronous mode)
Can use a snapshot for Read-Only of Mirror instance

20. Cons Replication Log Shipping Mirroring Complex setup
Publications can expire
Transactions can experience backlog/blocking
Manual Failover
Log Shipping
Asynchronous Only
Mirroring
Single Database Only
Physical Distance issues

21. Contrast Availability of data Time and effort to failover
Fully Recovered vs. Read-Only
Time and effort to failover
Automatic vs. Manual
Number of databases supported
One vs. Many

22. Summary Any of these are viable High Availability solutions
Make a list of questions and ensure Management is in agreement with the answers
Consider the available hardware and additional resources required

23. Resources http://www.sqlbackuprestore.com/introduction.htm

24. Where to Find Me Wendy.Pastrick@sqlpass.org @wendy_dance on Twitter
Blog: wendyverse.blogspot.com