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I currently have Mirroring set up between two production SQL Servers. One of these servers is a hardware SQL server (principal) and the mirror is a VM (on different server). I need to migrate these servers to Availability Groups (HA cluster NOT using shared storage).

None of this is my choice. I would personally prefer two VMs, or completely identical systems.

My question is: has anyone come across issues for AG/clustering between a hardware SQL Server and a VM SQL Server? Or is there any issues that you can imagine with that setup?

I have had no issues with Mirroring between a hardware & VM. As long as the servers are very similar (ie: same version of SQL Server, same RAM given, data files are named & stored in the same locations, etc). My concern is AG utilizes windows failover clustering - an unfamiliar territory for me - so I'd like to know if there's anything additional to look out for.

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  • Assuming your systems meet the requirements for clustering and AGs, there should be no issues. If there are any issues, they are defects and need to be fixed.
    – Tony Hinkle
    Dec 4, 2017 at 17:40
  • I thought so too, I guess I've seen some awful behavior from mirroring when ram wasn't the same on both servers...and wanted to know if there was any gotchas with this
    – Dina
    Dec 5, 2017 at 15:14
  • If the performance was poor, it wasn't because the amount of RAM was different, it was because the amount of RAM on one or both servers was inadequate. Microsoft always recommends the same amount of RAM, CPUs, disk speed, etc. on cluster nodes so that you'll (hopefully) get the same performance regardless of which server is running the workload. They just don't want to tell customers that they can run skinny on the "DR" node and then have the customer complain about performance when they have to run on that node.
    – Tony Hinkle
    Dec 5, 2017 at 15:19
  • It wasn't a performance issue but weird behavior like random failovers. It went away tho, either because we put identical ram on both servers or because of a patch.
    – Dina
    Dec 5, 2017 at 15:27

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I have had no issues with Mirroring between a hardware & VM. As long as the servers are very similar (ie: same version of SQL Server, same RAM given, data files are named & stored in the same locations, etc).

Then it should be exactly the same for Availability Groups. You shouldn't see a difference.

My concern is AG utilizes windows failover clustering - an unfamiliar territory for me - so I'd like to know if there's anything additional to look out for.

The biggest thing is quorum. In mirroring there was the option to use a witness instance for HA which sort of but not really acted like quorum. I say sort of because it didn't really vote because there could only ever be two instances in mirroring. Availability Groups rely on WSFC (except read-scale AGs, though they can have an optional metadata instance - and anything on Linux) which means there will be voting to determine quorum.

Here is a small introductory, there is more out there but this should give you an idea what you'll want to research.

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