One of the main features of Rockstor, by the way of BTRFS, is the ability to take Snapshots of Shares. Snapshots can be taken on demand or can be scheduled to be taken periodically. But say, we have a Share exported out to clients via Samba. How does a client, in this case a Windows user, access not only the contents of the Share but also the contents(individual files) of it’s Snapshots? It can be very useful to retrieve previous versions of a file, for example.

In the Windows world, this feature is called Shadow Copy. The server side of this feature is what Rockstor supports by using Samba’s vfs_shadow_copy2 which understands BTRFS Snapshots and exposes them to Windows clients as shadow copies.

Just like adding any other Samba export, go to the Samba screen under the Storage tab of the Web-UI and click on Add Samba Export button. Select Enable Shadow Copy checkbox and fill out the Snapshot prefix field. You should choose the Snapshot prefix field to be unique enough that it will not clash with directory or filenames. Eg: SNAPSHOT. The rest of the input in the form is same as it would be for any other Samba export.

We need to schedule Snapshots for the Share exported in the above step. We can do this by going to the Scheduled Tasks screen under the System tab and clicking the Schedule a Task button. The important input parameter here is the Snapshot prefix. It must be the same string from the previous step. Eg: SNAPSHOT. Choose rest of the input according to your needs.

The previous step results in periodic Snapshots for the Share that is exported via Samba in Step 1. The binding factor between Steps 1 and 2 is the Snapshot prefix input variable. All that is left now is to access the Share from Windows.

As the time goes by, files are added, edited and deleted from the Share by the client. Meanwhile, Snapshots are taken on Rockstor periodically and result in Previous versions or Shadow copies for files. To access previous versions of a file from Windows, go to it’s Properties window and click on Previous Versions tab.