Thanks so much for the detailed reply. I have about 20TB of data on the disks otherwise I would take your advice to set up a different scheme. Luckily, as it's a backup server I don't need maximum speed. I set it up with mergerfs and snapraid because I'm essentially recycling old drives into this machine and that setup works pretty well for my situation.

The proxmox host is the default (ext4/lvm I believe). The drives are also all ext4. I very recently did a data drive upgrade and besides some timestamp discrepancies likely due to rsync, the SCSI semi-virtualized thing wasn't an issue. I replaced the old drive with a larger one, hooked the old one up to a usb dongle and passed it through to OMV and I was able to transfer everything and get my new data drive hooked back into the mergerfs pool and snapraid. I'll do a test and see if I can still access the files directly in the proxmox host just for educational purposes.

I'll try to re-mount the NFS and see where that gets me. I'm also considering switching to a CIFS/SMB share as another commenter had posted. Unless that is susceptible to the same estale issue. I won't be back at that location for about a week so I might not have an update for a little while.