1. A Technical Overview of Microsoft® SQL Server™ 2005 High Availability Beta 2
Matthew Stephen IT Pro Evangelist (SQL Server)

2. What We Will Cover Barriers to availability
Database server failure or disaster
User or application error
Data access concurrency limitations

3. Barriers to Availability Overview
Business requirements
Time and location
Processes
Expectations
Technology
Hardware
DBMS software
Application software

4. Barriers to Availability Primary Server or DBMS Barriers
Database failure or disaster
Hardware failure
Human-made disaster
Natural disaster

5. Barriers to Availability Primary Server or DBMS Barriers
User or application error
Accidental data modifications
Malicious data modifications
Data access concurrency limitations
Multiple transactions accessing same data
Persistent data structure changes

6. Database Server Failure or Disaster Overview
Failover clustering
Database mirroring
Peer-to-peer replication
Comparison of other alternatives
Standard replication topologies
Log shipping
Backup and restore
Detach, copy, attach

7. Database Server Failure or Disaster Failover Clustering
Provides a hot standby
Built on Microsoft Cluster Services (MSCS)
Multiple nodes (Now 8)
Automatic failover of instance (~20 seconds)
Certified hardware required
Zero committed work loss
Single copy of instance databases
Standby not available for any other use
Supports more SQL services
MS-2087 Implementing Microsoft Windows 2000 Clustering

8. Database Server Failure or Disaster Failover Clustering
Shared Disk Array
2nd Private ‘Heartbeat’ network
Clustered Servers
Clients
Virtual Server
Primary Network

9. Database Server Failure or Disaster Database Mirroring
Provides a hot standby (instant)
Database failover
Very fast automatic failover (less than 3 seconds)
Transparent client redirect
Zero committed work loss
Some performance impact
Maximum one mirror for each database
Standby not directly available for any other use
MS-2733 Updating Your Database Administration Skills to Microsoft SQL Server 2005

10. Database Server Failure or Disaster Database Mirroring Hardware
No special hardware required
Requires a second server
Servers do not need duplicate hardware
Virtually no distance limitations
No shared disk arrays
Transaction latency requirements determine acceptable network latency
MS-2733 Updating Your Database Administration Skills to Microsoft SQL Server 2005

11. Database Server Failure or Disaster Database Mirroring With Automatic Failover
Separate Disk Arrays
Principal Server
Mirror Server
Clients
Witness Server

12. Database Server Failure or Disaster Database Mirroring With Automatic Failover

13. Database Server Failure or Disaster Peer-to-Peer Replication
Provides a hot standby of publication(s)
Can replicate entire database
Improved performance
No distance limitations
Some committed data loss
No conflict detection
MS-2733 Updating Your Database Administration Skills to Microsoft SQL Server 2005

14. Database Server Failure or Disaster Fault Tolerance with Peer-to-Peer Replication

15. Database Server Failure or Disaster Load Balancing with Peer-to-Peer Replication

16. Database Server Failure or Disaster Peer-to-Peer Replication Topology

17. User or Application Error Comparison of High Availability Options
Feature
Hot Standby
Warm Standby
Cold Standby
Database Mirroring
Failover Clustering
Peer-to-Peer
Transactional Replication
Log
Shipping
Backup / Restore
Detach / Copy / Attach
Data Loss
No data loss option
No data loss
Some Data Loss possible
Some data loss possible
Some data loss likely
Automatic Failover
Yes
Optional No
Transparent to Client
Yes, Auto-Redirect
Yes, Reconnect to same IP
No, NLB helps
Downtime
< 3 Seconds
20 Sec + DB Recovery
None
Seconds
Seconds + DB Recovery
Detect, Restore, Manual failover
Detect, Attach, Manual failover
Standby Read Access
Continuously accessible Snapshot
Continuously accessible
Intermittently accessible

18. User or Application Error Comparison of High Availability Options
Feature
Hot Standby
Warm Standby
Cold Standby
Database Mirroring
Failover Clustering
Peer-to-Peer Replication
Transactional Replication
Log
Shipping
Backup/ Restore
Detach/ Copy/ Attach
Data Granularity
Database Only
All System and User Databases
Table or View
Masks Disk Failure
Yes
No, Shared Disk
Special Hardware Needed
No, Dup. system needed
Specialized Hardware from Cluster HCL
Complexity
Some
More

19. User or Application Error Overview
Database snapshots
Database snapshot scenarios

20. User or Application Error Database Snapshots
Read-only
Static view of database
Transaction consistent at point of time
Does not store all data pages
Reads only original data pages
Reads data from snapshot if data has changed
Reads data from database if data has not changed
Increases disk I/O of source database
MS-2733 Updating Your Database Administration Skills to Microsoft SQL Server 2005

21. User or Application Error How Database Snapshots Work

22. User or Application Error Database Snapshot Scenarios
Enabling mirroring database for reporting
Historical point-in-time reporting
Recovering from administrative error
Protecting against application or user error

23. Data Access Concurrency Limitations Overview
Pessimistic concurrency controls
Optimistic concurrency controls
Snapshot isolation level
Read committed (Snapshot)
ONLINE index operations

24. Data Access Concurrency Limitations Pessimistic Concurrency Controls
Default Setting and Behavior
Designed for Data Integrity
SELECT Operations Require Shared Resource Locks
Different Isolation Levels Control Behavior of Shared Locks
MS-2072 Administering a Microsoft SQL Server 2000 Database

25. Data Access Concurrency Limitations Optimistic Concurrency Controls
Optional setting and behavior
Implemented using row versioning
Designed for data integrity but allows reads of committed data
SELECT operations do not require shared resource locks
Different isolation levels control behavior of committed reads

26. Data Access Concurrency Limitations Row Versioning
Several Uses
Triggers for Inserted and Deleted tables
Multiple Active Result Sets (MARS) sessions
ONLINE Index Operations
Optimistic concurrency controls (row snapshots)
Versions built in tempdb for all modified rows
Versions deleted when no remaining transaction or operation needs them

27. Data Access Concurrency Limitations Snapshot Isolation Level
Reads committed data at time of transaction start
ALLOW _SNAPSHOT_ISOLATION database option
TRANSACTION ISOLATION LEVEL SNAPSHOT session option

28. Data Access Concurrency Limitations Read Committed (Snapshot)
Reads committed data at time of statement
READ_COMMITTED_SNAPSHOT database option
TRANSACTION ISOLATION LEVEL READ COMMITTED session option

29. Data Access Concurrency Limitations ONLINE Index Operations
Table accessible for reads and modifications during ONLINE index operations
Existing non-clustered indexes available to optimize during ONLINE clustered index operations
Non-clustered index is not available during its index operation

30. Data Access Concurrency Limitations ONLINE Index Operation Commands
CREATE INDEX
ALTER INDEX
DROP INDEX
ALTER TABLE
ADD or DROP of UNIQUE index
ADD or DROP of PRIMARY KEY with CLUSTERED index option

31. Data Access Concurrency Limitations ONLINE Clustered Index Creation Operation

32. Session Summary
Several new features available in SQL Server 2005 to protect against server failure
Database snapshots can be used to protect against application, user, or administrative error
Use the new optimistic concurrency controls and ONLINE index operations to reduce database contention issues