Snapshots

The pISO supports the ability to 'snapshot' a virtual drive. Snapshots can be 'plugged in' just like a normal virtual drive, but will always be read-only. To create a snapshot, follow the steps below:

1. Open the 'Options' menu and select 'Snapshot Drive'

2. Select the drive you wish to snapshot from the list

3. You should now see a new drive with '-backup' after the name. This is the snapshot drive. It can be 'plugged in' or deleted like any other drive.

Performance

You may have noticed that the snapshot operation was instant. This is possible because the pISO is not actually copying any data to make the snapshot. Instead, whenever new data is added or existing data is changed on a drive that has a snapshot, the old data will be copied. This allows very fast snapshots, but means that adding or changing data on drives that a snapshot will be slower. This performance impact will increase as you take more snapshots of a drive. For this reason, we recommend against taking multiple snapshots of a drive.

Snapshot Lifetimes

Currently, snapshots will become invalid if you run out of space on your pISO. This can happen in the following way (with a 32GB SD card).

1. Create a virtual drive that is 100% of the SD Card (so about 32GB)
2. Add some data and snapshot the drive
3. Remove the old data and fill up the virtual drive with new data

Now the entire SD card is full, but there is still a snapshot that should contain the old data. This snapshot became invalid once there was no longer space to fit the old data. An error will occur if a user attempts to 'plug in' the virtual drive. Any data in the snapshot is lost.

In the future, we hope to prevent the user from invalidating snapshots like this, but for the time being, users should be cautious when mostly filling drives while maintaining snapshots.