Readable Secondary AG databases internally use snapshot isolation under the covers. This will enable read-only workload to run against secondary databases.
Total : 6 – 7
1 for WSFC cluster network name
1 for SQL Server instance network name
2 (1 on each node) for private/internal/heartbeat network among cluster nodes
2 (1 on each node) for public network access
1 for MSDTC (if MSDTC is configured as clustered service)
2 (1 for each node) for iSCSI HBA/network adapter for communication to SAN (if iSCSI SAN is used).
HBA is used for offloading iSCSI TCP/IP traffic processing from CPU
Queue Depth is the number of I/O requests (SCSI commands) that can be queued at one time on a storage controller. Each I/O request from the host’s initiator HBA to the storage controller’s target adapter consumes a queue entry. Typically, a higher queue depth equates to better performance.
Reports information about Windows users and groups that are mapped to SQL Server principals but no longer exist in the Windows environment.
If the orphaned server-level principal owns a database user, the database user must be removed before the orphaned server principal can be removed.