Thanks Jeffrey. Does it take more time to recover the databases in alwayson ag or fci failover or is it the same process.
Alwayson and FCI

Experts,
Understanding is that a FCI would take more time to failover vs AlwaysOn because of the SQL Instance restarting and the realignment of disks on the Secondary Node but if the realignment of disks and Instance restart on the other node happens in say 30 seconds, can we say that difference between the failover of the two(FCI and AwlaysOn) with along recovery of all databases is approx 30 seconds.
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Vishal 1,351 Reputation points
2021-07-09T16:11:13.36+00:00 Yes thanks, that is right AlwaysOn refers to Availability group
Alex Bykovskyi 876 Reputation points2021-07-11T07:41:34.43+00:00 Hey,
Always On Availability Groups should failover quicker than FCI. It is due to architecture. In synchronous commit mode you have at least to replicas running (primary and secondary), and failover occurs within seconds. https://www.sqlshack.com/explore-failover-types-in-sql-server-always-on-availability-groups/
In FCI in case of failover the role will start on another server, which will take more time. In addition, SQL FCI requires shared storage such as SAN or any kind of SDS. StarWind VSAN can be used as a shared storage option. Might help:
https://www.starwindsoftware.com/resource-library/starwind-virtual-san-installing-and-configuring-sql-server-2019-tp-failover-cluster-instance-on-windows-server-2016/Cheers,
Alex Bykovskyi
StarWind Software
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Seeya Xi-MSFT 15,191 Reputation points Microsoft Vendor2021-07-12T10:10:04.017+00:00 Hi @Vishal ,
As for the differences between FCI and AG, please refer to this: Comparison of Failover Cluster Instances and Availability Groups.
For the Comparison,
https://www.sqlservercentral.com/forums/topic/fci-vs-always-on-ag
https://dba.stackexchange.com/questions/196793/alwayson-ag-versus-fci
AlwaysOn Availability Group and AlwaysOn Failover Instance are the two provisions that enable the users to increase the availability of SQL Server instance. Both the provisions have their associated advantages and limitations.Best regards,
Seeya
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In an FCI - you can reduce the amount of time it takes to reallocate the drives from one server to the other using Cluster Shared Volumes.
https://learn.microsoft.com/en-us/windows-server/failover-clustering/failover-cluster-csvs
https://techcommunity.microsoft.com/t5/failover-clustering/cluster-shared-volume-csv-inside-out/ba-p/371872
The failover only takes as long as it takes to start SQL Server and recover the databases. It is the recovery of the databases that take the most time.