SQL Server 2008 R2Implementing High Availability

High availability ChallengeUptime SLA Downtime Per

YearDowntime Per Month

99.9% 8.76 Hours 43.8 Minutes

99.99% 52.6 Minutes 4.38 Minutes

99.999% 5.26 Minutes 0.438 Minutes

SQL Server 2008 R2 High Availability Goals Hardware Failover Clustering Database Mirroring Replication Log Shipping

Goals for High Availability Second copy of our data Have Real time or Near Real time switch

over Second copy – Updated Frequently Reduce workload – Automatic Switch

over to the second database

Less downtime for our users

Techniques available Hardware Failover clustering Database Mirroring Replication Log Shipping

Hardware Redundant Power supplies RAID Arrays Redundant CPU Power Redundant Network Cards SCSI/SAN Controllers

Key is redundancy

Node A

SQL Server failover clustering

Node B

Nodes

Clients

H/W H/W

Active - Passive

SQL Server failover clustering

Nodes A

Clients

Node A

H/W

Node B

H/W

Active - Active

Nodes B

A

C

DB

SQL 1

SQL 2

SQL 3

SQL 4

SQL 5

SQL 6

SQL 7

SQL 8

SQL 1(Principal)

A

B

SQL 2(Mirror)

A(copy)Transaction

Clients

SQL Native Client

Database Mirroringo Hot Standby protects against database or server failureo Provides a fault-tolerant database o Cost effective as no specialized hardware is requiredo Straightforward setup and administrationo Automatic or manual failover

o SQL Server 2008 R2 does not require a database restart after manual failover

o No shared components; two separate copies of datao SQL Server 2008 compresses the log stream from

principal to mirror

Database Mirroring Several different modes available It works on per database, clustering is per

instance basis Interaction with other database features which

involve storage outside database Log shipping Full text catalogues Database snapshots Replication

Does not support FILESTREAM Need to create server logins

Replication

Transactional Merge Replication Snapshot Replication

There is no built in type of Failover

A

C

B

Tokyo

New Delhi

New York

Clients

Replication High performance ─ latency measured in

seconds Minimal load on the server Cost effective as no specialized

hardware is required Straightforward setup and

administration Subscriber is accessible Used mainly for Scalability

SQL 1

A

B

SQL 2

A(copy)

Transaction Log Backup

Transaction Log Backup

Clients

Log Shipping Not Real-time Less Resource Hungary on Servers Supports FILESTREAM Provides database redundancy

Every some [Time]

Filestream

Log Shipping Cost effective as no specialized

hardware is required Straightforward setup and

administration Running read operations

such as reports on asecondary server is permitted

Users are disconnected when logrestore occurs

Log Shipping Can maintain multiple secondary servers Records history and status of backup/restore

jobs May set up to raise alerts when jobs fail

SQL Server 2008 R2 High Availability Goals Hardware Failover Clustering Database Mirroring Replication Log Shipping

Thank you and Q.A.