Synthetic full with transform, need for defrag/compact?

[mxx]

Hi,

I'm unable to find any answers on this, strangely enough.
When using forward incremental jobs with active full backups, compacting isn't needed, but won't the creation of synthetic full backups in forever incremental jobs (+ transformation of previous forward incrementals) also make compacting superfluous (since a new vbk is created)?
Also, just to make sure: I need at least 1x <full backup size> free space to use this feature, correct?

Thank you!

[foggy]

Yes, compact is mostly useful in case of forever forward incremental and reverse incremental backup methods, since they incur full backup file transformation and fragmentation. And yes, you need an additional space for the new full backup.

[mxx]

Thanks for your answer!
I'm confused though.. I understand why reverse incrementals would need this because no new full vbk is created, but I thought that synthesizing a new full backup would create a new compacted vbk anyway.
Or is it just like that, when at the same time the new vbk is being created, transformation happens?

[foggy]

Sorry, I'm not getting the question, could you please elaborate? What I was saying was that forever incremental with periodic synthetic fulls (that you're using) doesn't require compact operation to be performed, while forever forward incremental does.

[mxx]

That was partly a misunderstanding then.
But what I was referring to was forward incremental +periodic synthetic fulls + "transform previous backup chain" activated.

While you get a message saying that it's unnecessary to activate compacting when periodic synthetic fulls are enabled, this message is missing when you additionally activate transformation.

I would imagine that, transformation happening at the same time the synthetic full is being created, would be possible without letting the new vbk getting fragmented as it's not an old file that is being modified/injected.

So... were you referring only to synthetic fulls or also to synthetic fulls combined with transformations?

Thanks and sorry for the poor explanation.

[foggy]

Transformation of the chain into rollbacks works differently than simple synthetic full without transform. It transforms the existing full without creating a new one (as in case with synthetic full), so in this case compact operation can also be required.

Sorry for misunderstanding from my side as well.

[mxx]

I see, everything's clear now

Thank you for your time and the excellent support!