Replication Tasks: Issue when not replicating all snapshots?

TrueNAS General
1

I have two Truenas set up (A and B):

Truenas A takes periodic snapshots every six hours (1 am, 7am, 1 pm, 7 pm).

I have a replication task on Truenas B: It is set to replicate the 1 am snapshots from Truenas A. Will I be able to restore my data in case Truenas A gets destroyed?

I’m trying to wrap my head around the following: If each snap shot just stores the incremental changes that have been made, it would therefore be logical that you need each an every snapshot to restore. However, when re-searching the topic, I read that each snapshot represents the full filesystem state at that moment. I’m not sure how that is possible if each snapshot just saves the incremental changes that happened.

Also, in a youtube video from “Lawrence Systems”, the guy mentions that you need to have every snapshot that was taken or you might have a problem with the replication task.

See bellow for mentioned youtube video.
Should start at: 13:07

Any help is appreciated.

2

Each snapshot contains all data present at the time the snapshot was taken.

No need to worry.

A set of consecutive snapshots takes only as much disk space as necessary for

  • the first one with “all” data
  • the differences to get from the first to the second, third, …

But if you delete the first one, the data will not be deleted but will now be in the formerly second one. Etc.

Here’s a great walkthrough by forum regular @winnielinnie: