My division is is doing an upgrade from SQL Server 2008R2 with mirroring to SQL Server 2017 with clusterless availability groups. Until recently the testing has surfaced no issues or red flags. Then we installed CU1, had issues, uninstalled CU1 and the issues went away. The OS is server 2016 with the latest patches.
Observed behavior after CU1:
Using either SSMS or tsql we could create a 2 replica clusterless synchronous availability group, and add one database to it. The group could be failed over multiple times without issue. Ah, but add a second database and issues would arise on the failovers. One of the databases would invariably wind up in a not synchronizing state. No amount of fiddling could resurrect it. If I dropped and recreated the whole thing, it might be the other database that went to not syncing. A pertinent error message in the logger was "Failed to update Replica status due to exception 35222." This seems to be a message related to clusters, but since we are clusterless I was confused. After we uninstalled CU1 on both replicas, I was able to create the AG and add 22 databases (including the two original). Failovers were without issue. On a side note, automatic seeding did not always work with multiple databases. The operation would fail with a "Seeding Check Message Timeout". Dropping those databases from the AG and adding them one at a time was successful.
My question is:
Has anyone else experienced issues with clusterless AGs after CU1? If so, were you successful where I was not?
I thought CUs were going to be tested at the same level as SPs. While I know that bugs creep in no matter how thorough the testing, having this happen on the first one is troubling. It will cause us to really stress test each CU before deploying, which will mean we do not deploy them as they come out. We will deploy them only when we think there is a need to. We are a small organization without a dedicated dba, and need to be selective about what take on.