In a situation when Windows Server 2016 Hyper-V is supporting Windows Server 2019 guest VMs with CNA adapters and MPIO, when paths are disconnected the connection is intermittent. I/O starts to fail when MPIO path failover occurs.
This is a known issue.
A typical system configuration is similar to those in the Repro Steps which follow.
Configure a Windows 2016 Hyper-V system with a Windows 2019 guest:
- Configure multiple FC LUNs and present them to the Hyper-V system and have the Hyper-V system present these LUNs to the 2019 guest.
- Use a storage IO generation tool to run IO to all FC LUNs on the 2019 guest.
- Disable one CNA port.
- Wait 30 Seconds.
- Enable the CNA port.
- Wait 2 minutes.
- Repeat the port disables/enables above, test failures will be intermittent.
An IRP field being zeroed out at a lower level is being accessed while resubmitting at the MPIO level, causing the failures.
The issue has been addressed with Windows Server 2019 in the Windows Server 2019 July Rollup.