Tips for High Availability SQL Server Environments with ActiveCluster
Tip 1: Use Synchronous Replication for Zero RPO/RTO Why it matters: ActiveCluster mirrors every write across two FlashArrays before acknowledging the operation to the host. This ensures zero Recovery Point Objective (RPO) and zero Recovery Time Objective (RTO), which are critical for maintaining business continuity in SQL Server environments. Best Practice: Keep inter-site latency below 5 ms for optimal performance. While the system tolerates up to 11 ms, staying under 5 ms minimizes write latencies and transactional slowdowns. Tip 2: Group Related Volumes with Stretched Pods Why it matters: Stretched pods ensure all volumes within them are synchronously replicated as a unit, maintaining data consistency and simplifying management. This is crucial for SQL Server deployments where data, log, and tempdb volumes need to failover together. Best practice: Place all volumes related to a single SQL Server instance into the same pod. Use separate pods only for unrelated SQL Server instances or non-database workloads that have different replication, performance, or management requirements. Tip 3: Use Uniform Host Access with SCSI ALUA Optimization Why it matters: Uniform host access allows each SQL Server node to see both arrays. Combined with SCSI ALUA (Asymmetric Logical Unit Access), this setup enables the host to prefer the local array, improving latency while maintaining redundancy. Best practice: Use the Preferred Array setting in FlashArray for each host to route I/O to the closest array. This avoids redundant round-trips across WAN links, especially in multi-site or metro-cluster topologies. Install the correct MPIO drivers, validate paths, and use load-balancing policies like Round Robin or Least Queue Depth. Tip 4: Test Failover with a regular cadence Why it matters: ActiveCluster is designed for transparent failover, but you shouldn’t assume it just works. Testing failover with a regular schedule validates the full stack, from storage to SQL Server clustering and exposes misconfigurations before they cause downtime. Best practice: Simulate array failure by disconnecting one side and verifying that SQL Server remains online via the surviving array. Monitor replication and quorum health using Pure1, and ensure Windows Server Failover Clustering (WSFC) responds correctly. Tip 5: Use ActiveCluster for Seamless Storage Migration Why it matters: Storage migrations are inevitable for lifecycle refreshes, performance upgrades, or datacenter moves. ActiveCluster lets you replicate and migrate SQL Server databases with zero downtime. Best practice: Follow a 6-step phased migration: 1. Assess and plan 2. Set up environment 3. Configure ActiveCluster 4. Test replication and failover 5. Migrate by removing paths from source array 6. Validate with DBCC CHECKDB and application testing This ensures a smooth handover with no data loss or service interruption. Tip 6: Align with VMware for Virtualized SQL Server Deployments Why it matters: Many SQL Server instances run on VMware. Using ActiveCluster with vSphere VMFS or vVols brings granular control, high availability, and site-aware storage policies. Best practice: Deploy SQL Server on vVols for tighter storage integration, or use VMFS when simplicity is preferred. Stretch datastores across sites with ActiveCluster for seamless VM failover and workload mobility. Tip 7: Avoid Unsupported Topologies Why it matters: ActiveCluster is designed for two-site, synchronous setups. Misusing it across unsupported configurations like hybrid cloud sync or mixing non-uniform host access with SQL Server FCI can break failover logic and introduce data risks. Best practice: Do not use ActiveCluster between cloud and on-prem FlashArrays. Avoid non-uniform host access in SQL Server Failover Cluster Instances. Failover will not be coordinated. Instead, use ActiveDR™ or asynchronous replication for cloud or multi-site DR scenarios. Next Steps Pure Storage ActiveCluster simplifies high availability for SQL Server without extra licensing or complex configuration. If you want to go deeper, check out this whitepaper on FlashArray ActiveCluster for more details.
