[pve-devel] TrueNAS over iSCSI: Snapshot Management

[Max R. Carrara]

On Mon Oct 6, 2025 at 3:09 AM CEST, Lorne Guse wrote:
> [...]

Hi Lorne, hi Morgan!

Sorry—only now finally got some time to look into this.

Regarding multi-generational snapshot rollbacks: That is something
that's possible actually; our `lvm-thin` storage supports that, for
example [0]. You're probably running into the default implementation [1],
hence the error.

We don't support it for our ZFS pool storage though [2] (and thus also
not for the ZFS over iSCSI storages), since `zfs rollback` doesn't
support it without destroying intermediate snapshots [3].

The user can still do rollbacks on older snapshots, they just have to
delete the intermediate ones first, in this case. (So basically what
`zfs rollback` requires one to do.)

With all that being said, I agree with Morgan here; it's best to just
let PVE manage the snapshots and whatever contents are on the volume, as
it is a cleaner experience for the user. (Principle of least surprise
and all that.)

Hope that helps! If you need anything else, feel free to ping me! (:

[0]: https://git.proxmox.com/?p=pve-storage.git;a=blob;f=src/PVE/Storage/LvmThinPlugin.pm;h=ccefd0eb24630a4ae5e206002760126dfce9304a;hb=refs/heads/master#l366
[1]: https://git.proxmox.com/?p=pve-storage.git;a=blob;f=src/PVE/Storage/Plugin.pm;h=2291d72d929b9de83f7703aae146372e4b663860;hb=refs/heads/master#l1325
[2]: https://git.proxmox.com/?p=pve-storage.git;a=blob;f=src/PVE/Storage/ZFSPoolPlugin.pm;h=3b3456b7482ad4388a757e80484412384a677da1;hb=refs/heads/master#l551
[3]: https://openzfs.github.io/openzfs-docs/man/master/8/zfs-rollback.8.html