1. SQL AlwaysOn Availability Groups
Tomislav Balaž

2. Sadržaj Što je AlwaysOn Availability groups Feature?
Koristi koje nam donosi AlwaysOn
FCI vs AO
Database Mirroring vs AO
Preduvjeti
Napomene
Novo u SQL 2016
Demo

3. Što je AlwaysOn Availability Groups Feature?
AlwaysOn Availability Groups feature is a high-availability and disaster-recovery solution that provides an enterprise-level alternative to database mirroring.
Dostupan je od verzije 2012
Potrebna verzija je Enterprise

4. Kakve koristi nam donose AG
Jedna primarna Availability replica i do osam secondary Availability replica
Synchronous i Asynchronous commit mode
Tri tipa failover-a
Active secondary replica (Read-only ili Backup)
Availability Listener za svaku AG
Failover Policy
AlwaysOn Dashboard i PowerShell cmdlets
Replica je instanca baze na drugoj instanci SQL servera
Asynchronous-commit mode. This availability mode is a disaster-recovery solution that works well when the availability replicas are distributed over considerable distances.
Synchronous-commit mode. This availability mode emphasizes high availability and data protection over performance, at the cost of increased transaction latency. A given availability group can support up to three synchronous-commit availability replicas, including the current primary replica.
automatic failover, planned manual failover (generally referred as simply "manual failover"), and forced manual failover (generally referred as simply "forced failover")
U SQL serveru 2016 moći ćemo definirati failover ako je baza corruptana kroz AG health monitor (verzija 2014 gleda samo health SQL instance)
(str. 20)

5. Usporedba FCI vs AllwaysOn
Nodes within an FCI
Replicas within an availability group
Uses WSFC cluster
Yes
Protection level
Instance
Database
Storage type
Shared
Non-shared
Storage solutions
Direct attached, SAN, mount points, SMB
Depends on node type
Readable secondaries No
Applicable failover policy settings
WSFC quorum
FCI-specific
Availability group settings
Failed-over resources
Server, instance, and database
Database only

6. Usporedba Databse Mirroring vs AllwaysOn
Database Mirroring
AlwaysOn Availability Groups
Maximum number of secondary databases
1 Mirror
4 Secondaries
Requires Windows Clustering No
Yes, however the SQL Servers can be stand-alone
Automatic failover
Yes, requires witness server and high-safety mode
Yes, one
HA or DR
Choose one
Each secondary independently configurable
Groups of databases
No, each database is configured separately
Multiple databases can be grouped to failover together
Offload backups
Yes
Connection to active database
Requires special connection string for failover
Redirection handled by Windows Clustering with a virtual name. Special connection string not required
Connection string to mirror or secondary database
N/A
ApplicationIntent connection string to automatically redirect or can use traditional connection string with server name.

7. Preduvjeti Windows Server 2008 ili noviji SQL Server 2012
.Net framework 3.5.1
Node u WSFC
Hotfixes ako koristite Windows Server 2008 ili 2008R2
Ne na DC
Svi SQL serveri moraju imati isti collation
Enable AllwaysOn Availability groups
Link:
Checklist

8. Napomene Enterprise edition
Brisanje baze, gubitak data file-ova ili corruption transaction loga ne uzrokuju failover
Server configuration settings, Credentials, Jobs, Cros-Database queries, Linked servers…
System databases ne mogu biti dio AG
Baze moraju biti u Full recovery model
DB replike moraju biti na različitim nodovima u FC
Link:

9. Novo u SQL 2016 3 synchronous replicas for auto failover
Loadbalancing on read only replica
Automatic failover on database health
Link:

10. Setup 1. Create Cluster 2. Add nodes to cluster
3. Setup file share majority
4. Enable AllwaysOn
5. Create Availability Group
6. Backup database
7. Add database to Availability group
8. Failover

11. Demo 1. Availability group wizard 2. Read only replica
3. Backup replica
4. Test failover
Pokazati wizard i objesniti svaki dio wizarda.
Kreirati read only replicu
Pokazati backup on secondary
Pokazati failoverpolicy
Test failover

12. ?