Unable to Replicate Snapshot to Proxmox Backup

[Smaxbang`]

Hi. I am fairly new to Proxmox as well as ZFS please forgive me if I misuse any terminology. I have a TrueNas server that is hosting some datasets. I would like to replicate snapshots of those to PBS. I have already configured and successfully connected the two through SSH. However when I try to replicate the data I get the following error.

cannot unmount '/mnt/datastore/backup1': pool or dataset is busy
warning: cannot send 'pool1/ExperianBackup@auto-2024-04-18_00-00': signal received.

Which leads me to believe that I must have not configured my datastore on PBS correctly. I have two 1 TB HDDs and a 256GB SSD for the Boot and OS partitions. I configured the two HDDs in a ZFS mirror which created a single datastore backup1.

Searching the forums it seems like the ideal storage type for storing snapshots is a directory with is_mountpoint yes configuration. However, I cannot for the life of me seem to figure out how to do that with my current config. Is this possible to do. I would like to keep the redundancy the mirror provides. I fear I may be missing some crucial foundational knowledge. Any help would be appreciated.

 

[_gabriel]

Proxmox Backup Server has nothing to do with ZFS snapshots.

it does not work with ZFS send/receive features, it has its own file-based datastore to manage its snapshots.
https://pbs.proxmox.com/docs/technical-overview.html#datastores
its datastore can be stored on ZFS mainly for the integrity features.

 

[Dunuin]

I fear I may be missing some crucial foundational knowledge

Yes.

1.) Don't temper around with your datastore folder or PBS will complain. If you want to store any data not created by PBS, use another folder.
2.) ZFS snapshots are not files and a replication won`t copy files. A directory storage can only store files and isn't using any ZFS features.
3.) Replication from TrueNAS to PBS could be problematic later, as the OpenZFS version of TrueNAS is usually behind Proxmox products and replication is only backwards compatible. So you should avoid upgrading your ZFS pools so both support the same ZFS features and are compatible.
4.) As far as I understand the replication task of TrueNAS is there to replicate datasets and zvols between two TrueNAS servers. While it is possible to replicate data between pools directly using ZFS commands without any TrueNAS stuff (see "zfs send | zfs receive") ,so snapshots could replicated between TrueNAS and PBS, I'm not sure if replication tasks of TrueNAS will allow that.
5.) To replicate data from TrueNAS to PBS, you probably want to create a new dataset on PBS first that could act as your replication target and that is not on top of the datasets PBS created.

 

[Smaxbang`]

Its clear I have much to learn about ZFS and Proxmox. In the meantime it seems my best option would be to spin up another TrueNAS box and replicate the data there. Thank you both for your help I will do more research based on your suggestions.

 

[Hua Ngoc Hieu]

I will take advantage of the nature of file storage, by using Rsync for 2 linux environments.