Full backup file merge vs synthetic full

[markiboy1]

Hello. I have 2 different backup policy
1. 1st Backup policy - Under storage tab retention is 7 restore points and backup mode is incremental.
- create synthetic full backups periodically and active full backup are disable

2. 2nd Backup policy - Under storage tab retention is 7 restore points and backup mode is incremental.
- create synthetic full backups periodically is enable (every saturday)

I am wondering how the first policy is creating full backup even though any of synthetic full/active full backup option is disable. It seems that it is still merging all the incremental after 7 restore points.

Can someone help me understand the difference with this Full backup file merge vs synthetic full?

[filippoAdb]

According to my understanding in the first case the last full is always seven restore points old. Every backup chain starts with a full, then after 7 incremental it is out of retention and can be deleted, but the chain needs some parts of it, so it is merged with the oldest incremental that becomes a synthetic full.
In the second case you decide when the full backup is performed, for example on Saturday. That way on Sunday you have a full of the previous day and not 7 restore points older. I suppose in this case the restore points are at least 7, but they are a few more during the week, till 13/14, then 6/7 are deleted at the same time.

[Mildur]

Hello Mark

The first full backup is always required. When you disable regular full backups, the chain will be a forever incremental backup chain. As descripted by Filippo, the oldest incremental will be merged with the full backup file.
When you enable regular synthetic full backups, the chain will be a forward incremental chain. The Full backup won't be merged in this case. A new full backup file will be synthesized from a new incremental backup and existing backup files on the repository.

We provide an animation for both backup methods in our knowledge database:
https://www.veeam.com/kb1932


Best,
Fabian