AlwaysOn
In SQL Server 2012
Fadi Abdulwahab – SharePoint Administrator - 4/2013 http://blogs.msdn.com/b/fabdulwahab/
Terminologies
High Availability (Planned and Unplanned)
Disaster Recovery
Recovery Time Objective (RTO)
Recovery Point Objective (RPO)
Budget
Solutions in SQL Server
Backup and Restore
Log Shipping
Replication
Mirroring
SQL Cluster
AlwaysOn
Mix and Third parties
Backup and Restore
Can lose data
Inexpensive Solution for DR
No HA
Log Shipping
HA , DR
No Automatic Failover but automate the process of backup and restore
Database Level
Inexpensive solution
Log Shipping
Replication
Database , Object level
No automatic failover
Can use as Load balance
HA , DR
Replication
Mirroring
HA , DR
Automatic failover (need witness server – optional)
Read-only database for secondary
Mirroring
SQL Cluster
HA
Expensive solution ( HD , License ,..)
Server level
Include two nodes or more
Required SAN Storage
A/P , A/A ,A/A/P,…
Need DR (Log shipping , Backup and Restore,..)
No Load Balance ( Use Transactional Replication)
SQL Cluster
AlwaysOn
New Feature in SQL Server 2012
Can have 5 replicas (one Primary and four secondary servers)
HA , DR (enhancement for mirroring) and Read-only access
Can be sync and async ( No acknowledgement ,minimize the transactions)
No need for SAN storage (Not like SQL Cluster)
Can deploy geographical
Can use Secondary servers for backup and reporting access
Automatic failover
Types (Primary (R/W and send trans logs to secondary) and Secondary (R)
AlwaysOn
Windows Cluster is required
Interchangeable ( Transactions terminated)
Failover can be ( Automatic , Manual and forced (possible data lose in case of async) (by commands)
Support T-SQL and PowerShell
Diff Backup not supported for secondary
Secondary use snapshots to avoid any blocking
Support page repair
Client can connect direct , Ava group and Read-only routing
Read-only settings ( No , Read –intent only , Yes)
Database should be :
Not belong to any Ava. Group
Enable R/W
Enable Multi User mode
Full Recovery
Full backup
Not used by mirroring
Automatic Failover (up to 2) (Required Sync)
Sync (Up to 3)
Need DNS and Static IP ( can be DHCP)
Configuration (Full (same path – need backup ) – Join (Already restored) – skip (restore later
When SQL user added to Primary the user must created in secondary (except if use contained databases – New feature in SQL Server 2012)
Backup Options
Prefer (run on secondary except if primary not online)
Secondary only (Not support diff backup)
Primary only (support diff backup)
Any replica (based on factors)
Demo
Prerequisites ( Windows Cluster , 2 instances at least)
Configuration (Enable , Create Ava. Group and backup)
Add/Remove databases …
Add/Remove Replica…
Suspended and resume…
Dashboard and DMVs for monitoring
Q&A
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