zfs error: cannot destroy : dataset is busy

I just ran into the same issue with multipath as mackpaul1967 confirmed. I am concerned this will have adverse affects on replication, migration and/or backups. I had just emailed "office@proxmox.com" about multipath support and was told it was supported but not much detail. It might be a show-stopper for me, so if anyone has extra information I would greatly appreciate it.
 
I felt in the same pit. The trick is to blacklist all zvol devices in multipath.conf:

Code:
blacklist {
    devnode "^zd[0-9]*$"
}
 
I know this is a little old now but for those still struggling with this I was able to replicate and solve without rebooting. Make sure the container you are trying to delete is not included in the current backups, if it is go to Datacenter > Backup > Select the Backup entry and click on Edit, un-check the box for the container you want to delete and click ok. I followed this process and was able to delete the zfs vol without issues.
This worked for me, thank you. There was an orphan dataset for the CT# on the target node I was trying to replicate to (maybe a removed CT that never got cleaned up) and I couldn't remove it because it was "busy". Removed it from the backup jobs on the cluster and I could remove the dataset with the -r option to remove children as well. Then I could initiate the replication from the original node to the target, and add the CT back to the backup job for the cluster.