This documentation mentioned to not use NFS. Can NFS4 be used? I see some questions or examples with NFS for shared store. I have iSCSI block storage, is this something which could be used?
I have tried to use iSCSI, however it can be mounted on one VM at a time, I am trying to understand what is industry standard.
Using NFSv4 is perfectly viable, but it won't provided optimal performance.
The documentation you cited is outdated as it comes from 2.31.2. It says:
We do not recommend you use Network Attached Storage (NAS), e.g. NFS mounts to store any shared journal (NFS is slow).
The latest documentation (from 2.33.0 at this point) says this:
Network Attached Storage (NAS), like an NFS mount, is viable but won’t provide optimal performance.
If you can't find a way to use iSCSI on both brokers simultaneously then it definitely wouldn't be viable. The point of having a shared filesystem is that both brokers are able to use it.