Jason McKittrick's Blog

AlwaysOn 2014 Enhancements from AlwaysOn 2012

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

 

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