FreeNAS 11.3, multiple periodic snapshots and exporting shadow copies on a CIFS share

[dkas]

In earlier versions of FreeNAS, there was the option to select a specific periodic snapshot task for the shadow copies export. So we could basically create multiple periodic snapshot tasks (daily/10y, hourly/2weeks) and export only the smaller one to the CIFS share as a shadow copy.

Now in 11.3, the option to select a periodic snapshot in the CIFS share seems to be gone. Where in 11.2 there was still a drop-down menu in which we could select the periodic snapshot to be exported as a shadow volume, now there is only a checkbox:
[x] Enable Shadow Copies.

This has multiple very unfortunate consequences, the first and probably worst is that in a scenario like mentioned above, the sheer amount of shadow volume copies that will be exported can cause a serious strain on the NAS when they are called from a Windows client using the "Previous Versions" functionality.

Secondly, sometimes there are older snapshots of a share that we explicitly do not want to share over CIFS.

Is there any way to select a specific snapshot to be exported - or deny another one from being exported - that I am missing here?

 

[anodos]

In earlier versions of FreeNAS, there was the option to select a specific periodic snapshot task for the shadow copies export. So we could basically create multiple periodic snapshot tasks (daily/10y, hourly/2weeks) and export only the smaller one to the CIFS share as a shadow copy.

Now in 11.3, the option to select a periodic snapshot in the CIFS share seems to be gone. Where in 11.2 there was still a drop-down menu in which we could select the periodic snapshot to be exported as a shadow volume, now there is only a checkbox:
[x] Enable Shadow Copies.

This has multiple very unfortunate consequences, the first and probably worst is that in a scenario like mentioned above, the sheer amount of shadow volume copies that will be exported can cause a serious strain on the NAS when they are called from a Windows client using the "Previous Versions" functionality.

Secondly, sometimes there are older snapshots of a share that we explicitly do not want to share over CIFS.

Is there any way to select a specific snapshot to be exported - or deny another one from being exported - that I am missing here?

All ZFS snapshots will always be available to the user in one way or another if he is sufficiently savvy with his computer (if the snapshot directory is located within the root of the share). Removing from snapshot list is just a way of obfuscating available snapshots. Currently list is limited to snapshots where _used_ is greater than 0 (should limit to relevant ones). Iterating snapshots is unavoidable (zfs_iter_snapshots_sorted() is called to generate the list), but you can limit results by setting:
shadow:include = <list of snapshot names for inclusion> or shadow:exclude = <list of snapshot names for exclusion>. Wildcards such as * and ? are supported.

 

[anodos]

Snapshot list is cached by default for 5 minutes. Mappings for @GMT name to path in .zfs/snapshot is in a MRU cache capped at 1MB.