Some questions about Btrbk backup options and restoring

General system Applications
21

That is “differential”, not “incremental”

Incremental means only changed data is sent but it has no implications about how the data is stored or restored. Nor does it imply anything about “full” backups.

Btrfs snapshots are subvolumes. In the case of btrfs subvolumes, there is no concept of a “full” subvolume. The subvolumes can share data but they are all complete as of that point in time.

22

sorry, maybe I’m being stubborn but here’s chatGpt’s answers :

peux tu me traduire ma dernière question et ta réponse en Anglais ?

ChatGPT

Sure! Here’s the translation of your last question and my response in English:

Question: “Sorry, but I didn’t understand the difference between differential backup and incremental backup.”

Answer: "No problem, I’ll explain the difference between differential backup and incremental backup more clearly.

Differential backup and incremental backup are two backup methods that aim to save time and space by only backing up modified files. Here’s the distinction between the two:

  1. Differential Backup: A differential backup backs up files that have been modified since the last full backup. This means that during the first differential backup, all files modified since the previous full backup will be backed up. In subsequent differential backups, only files modified since the last differential backup will be backed up. Therefore, the size of the differential backup tends to increase over time as it includes all files modified since the last full backup.
  2. Incremental Backup: An incremental backup only backs up files that have been modified since the last backup, whether it was a full backup or an incremental backup. This means that during the first incremental backup, only files modified since the previous full backup will be backed up. In subsequent incremental backups, only files modified since the last backup, whether it was a full backup or an incremental backup, will be backed up. Therefore, the size of the incremental backup tends to increase at a slower pace compared to the differential backup, as it only backs up changes made since the last backup.

In summary, the main difference lies in the scope of the backup:

  • Differential backup backs up files modified since the last full backup.
  • Incremental backup backs up files modified since the last backup, whether it was a full backup or an incremental backup.

It’s important to note that to restore data from a differential or incremental backup, you will need the initial full backup as well as all the intermediate differential or incremental backups in chronological order."

==> whether Btrbk makes incremental (what he pretends to do) , or differential backups, if words are words, it requires the presence of a full backup to work.

Of course, the first incremental backup can be considered a differential backup, but not the ones that follow. I understand the difference

The webpage of the editor (claims to do incremental backup)

23

I mean…that just means chatgpt is incorrect. This shouldn’t be surprising.

Specifically, this part is wrong for both differential backups and incremental backups:

Differential backups are usually differential from the last full backup so you wouldn’t need the intermediate backups to restore.

And as discussed above over and over again, modern incremental backups simply don’t won’t work like that anymore. Feel free to take a peek at the documentation for most modern backup solutions. They will not describe incremental backups as described by chatgpt.

Incremental backups are defined by sending incremental data. They may or may not need a full to be restored. It depends on the implementation. Most modern implementations do not require the full anymore. This is because they are de-duplicating which is similar to snapshots.

24

okay editor site :

Step 1: Restore Backup

(skip this step if you restore from a snapshot)

# locally mounted backup disk
btrfs send /mnt/btr_backup/data.20150101 | btrfs receive /mnt/btr_pool/

# from / to remote host
ssh root@remote btrfs send /mnt/btr_backup/data.20150101 | btrfs receive /mnt/btr_pool/
btrfs send /mnt/btr_backup/data.20150101 | ssh root@remote btrfs receive /mnt/btr_pool/

Hint: Try to send-receive backups incrementally if possible. In case you still have common snapshot / backup pairs (i.e. both “snapshot_subvol” and “target_subvol” are listed above), use btrfs send -p <parent>.

From this point on, data.20150101 on both disks can be used as parents for subsequent send-receive operations, and a received_uuid relationship is established (see below).

  • the word incremental is a misuse of language ??
25

I am not sure what makes you think that?

26

you said it’s differential, they sould use the term differential then.

I got an headeache, i go to bed…

27

btrbk isn’t doing a differential backup. I wrote that your description described a differential backup.

28

@dalto , morning, I think we don’t understand each other…

They don’t do diiferential backup, they claim to do inceremental ones.

Is it true or not ?

Then I’ll considered the topic closed.

29

Two simple images would help you understand what they are.

Btrbk (btrfs send | btrfs receive), Borg, Restic and more different tools do incremental backup:
image

Differential backup:
image

30

I believe that what btrbk does is a form of incremental backups.

31

thanks for the confirmation guys.

That said btrbk seems very powerful, I’ll look into it.

32

This topic was automatically closed 2 days after the last reply. New replies are no longer allowed.