Recently one of my customer was looking for detailed information on SQL Server AlwaysOn 2014 Enhancements. Below is a good list of product enhancements that I put together listing enhancements in SQL 2014 AlwaysOn from what was available in SQL 2012. If you are looking to install a new version of SQL to get AlwaysOn setup from a legacy 2008 R2 or older version of SQL, it is worth it to jump to SQL 2014. The list I created below should help confirm that for you when designing the solution.
- Increased availability of readable Secondaries in multi-site environments
- Lasting Network outage between sites
- Helpful in Geo-Dispersed DR/HA
- Handle Loss of Quorum on WSFC
- Increased number of Secondaries
- 4 to 8
- Distribution of replicas in a geo-distributed environment
- Additional replicas can be deployed across the geo-distributed environment, allowing read workloads to run against a local replica.
- Use readable Secondaries despite network failures (important in geo-distributed environments)
- Scaling-outofread workloads
- Additional replicas can be used to load balance read workloads.
- Load balancing can be implemented using simple DNS round-robin or specialized (hardware or software) load balancing solutions. Good for heavy read workloads, searches.
- Reduce query latency (large-scale environments)
- Enhanced Diagnostics
- AlwaysOn XEvents in Dashboard
- Easier to find information when situations arise and enhanced monitoring
- Easier to correlate issues
- Simplified/Detailed Error messages and more detail at all levels
- Error Example: replica can’t become primary
- New: because replica is not synchronized
- New: because windows cluster was started in forced quorum mode
- New: because replica is a manual failover replica
- Etc…
- Information about the underlying Windows Server Failover Cluster in AlwaysOn DMVs.
- Support for Cluster Shared Volumes
- Shared Disks available to all nodes
- CSVs are supported on Windows Server 2012 and Windows Server 2012 R2 only
- Improves SAN storage utilization and management
- SAN Storage Utilization
- Increase resiliency of storage failover (abstraction of temporary disk-level failures)
- Avoid drive letter limitation (max 24 drives) via CSV paths