Veeam Backup - Syntethical Backup / Retention Policy

Hi
Find here the official explanation of retentions
https://helpcenter.veeam.com/docs/backup/vsphere/retention_policy.html?ver=120

I will try to give you some light,
When you select retention by days, doesn't matter the number of points, it counts days.

in your case / config, you will have F=Full i=incrementals
Fiiiiiiiiiiiii
When a Friday hits, it’ll be a Synthetic Full
Active Full First Friday of the month.

For a backup chain, the incremental are linked to a Full backup, so, as an example

Full - Synthetic Full - Active Full

FiiiSiiiAiiiii (14)

Sun Mon Tue Wen Thur Fri Sat

(Fiiii)SiiiiiiAiiiiiiSii

SiiiiiiAiiiiiiSii  This would be the remaining backups, taking into count we started on Sunday.

After all this, as you can see, there are 14 days, so the next one will be keep until the new full will come up, then, it will count the 14 days up to the next valid full, and when that premise is OK, it will delete the oldest backup point (day) keeping at least (minimum) the latest 14 days.

hopefully I give you some light, and not confused you more, or got it wrong.

cheers.

Thank you guys for clarification.



@haslund What is the main difference between Active Full vs Synth Full?
I’m using Synology NAS to store our backups, so Synth Full will be enough for that?

In which cases we need active full and in wich Synth Full

Active Full will extract all of your data from the production environment, this puts a larger load on the production systems and less load (from a certain perspective) on the backup storage. Of course, there will be more data written to the repository, however, there will not be any reads and all the writes will be sequential.

Synthetic Full reads almost all data from the currently active backup chain, and only any changes since the previous job run from the production environment. This means almost no load to the production environment, but a big load to the backup storage due to reads and writes.

For your environment with a Synology NAS (you didn’t clarify if you are using it as SMB or NFS or perhaps mounted it to a server via iSCSI).

If you had mounted it to a server using iSCSI and formatted the drive with ReFS, then I would say stick to synthetic fulls because ReFS supports fast clone and you could offload almost all load to the backup storage via the file system.

If you are using SMB or NFS, then using synthetic fulls puts a massive load on your backup storage and it will take a very long time to produce the full backup - typically much longer than making an active full. Additionally, from SMB and NFS there is a bigger risk of corruption and as such I would strongly suggest using active full backups periodically and just disabling synthetic fulls.

Here you can find a read about Active and Synthetic backups

https://helpcenter.veeam.com/archive/backup/95/vsphere/backup_methods.html

and some discussions from the forum

https://forums.veeam.com/veeam-backup-replication-f2/synthetic-full-backup-vs-active-full-backup-t52702.html

cheers.

Nice responses @haslund and @HunterLAFR 

 @haslund We have two locations: Austria and Serbia.
On both locations we have two Synology RS3621xs+ with 64TB.
Both of them we are using as SMB shares.

I tried while ago iSCSI but not using it anymore.
So in this scenario without synthetical would be the way to go

Yes sir, I would disable synthetic fulls and leave active fulls enabled.

I’m not sure how it will impact our production.
We have a FileServer which is arround 10TB, with synthetical backups it needs sometimes up to 4-5 days and that is not so quick, with Active Full it will take even more?

Trying to figure out what would be the fastest and most efficient way.
I’m not so strong with Veeam but expanding knowledge day by day.
Thanks to everyone.

We are doing synth full backups on Friday and I dont know if it will end until monday when our work is starting. 
As I can see Active Full Backups are going on the VM files directly where it is stored and it can load up traffic on production. I don’t want to slow down the File Server, it will be impossible to work then, because even with smaller network traffic increase our employees are not satisfied.

Excellent responses from @haslund and @HunterLAFR 

Hi @NemanjaJanicic -

Just following up on this retention post. I believe you received some great responses which helped answer your question. If one of the comments did indeed answer it for you, we ask you mark one as ‘Best Answer’ so others with a similar question who come across your post may benefit.

Thank you.