Wording: incremental vs. differential

Hi there,

while I was thinking a little about backup schedule and retention periode, I came about the restore and therefor about the wording.
Sure: if I restore a directory from the scratch, I will need all file backups beginning with the last full backup, so this is a real incremental.

But isn´t it right, that if I restore images from the cratch I have to restore the last full backup followed by the last “incremental” backup? So this would be a differential and not a incremental…

Cheers, Jochen

During restore all backups, image and file backups, behave like full backups, so you don’t have to care about that at all. The difference is what is transfered during the backups.

An incremental file backup only transfers the files changed since the last backup. A differential file backup would transfer all the files changed since the last full backup. Which would of course be sub-optimal.

But you are right: The image backups should be called differential, because there every image is based on the last full. This is done so the server can delete any incremental image backups, not just the last one in the chain. See here for the difference http://www.acronis.com/resource/solutions/backup/2005/incremental-backups.html .

[quote=“uroni”]During restore all backups, image and file backups, behave like full backups, so you don’t have to care about that at all. The difference is what is transfered during the backups.[/quote]I don´t fully agree that because for example you are able to set full backups every 30 days, incremental every day and minimum incremental backups to keep less than 30. In case of incremental backups (file) you really need all backups between full and restored session, but with that example settings I would have disabled myself to restore all files to a specific date even if the full backup was older than this date. Wouldn´t I?

No. For all intends and purposes except what gets transfered every file backup behaves like a full backup. You can even delete all full backups and the incrementals will still be complete.

I see that it is confusing – because why would you do a full backup then? Good question. If there is a bug in the way incrementals are done, full file backups give you some kind of backstop. Other reasons do not exist… (So you could set “Max number of full backups” to 1 and “Interval for full file backups” to a ridiculously high number).

How difficult problem be, that the deleted incremental backup was included in the full backup.
It is clear that this will overwrite files in the full backup.
The number of incremental backups would mean only change history files.
(How far to go back in history changed file)
I’m sorry my English is not good.

Hey, short question,

does this mean its enough to keep the last “incremental” Backup and if i restore that i have all the files restored?

This means for me it would be enough to keep the last 2 Incrementals. actual day for actual Data and the Day before as a “savepoint” if actual Incremental fails?

It would be a total waste of Diskspace to keep more than that…or am i missunderstanding this?

If im wrong pls explain exactly which BackUps are needed to restore properly.


Day 1 Full
Day 2 Inc
Day 3 Inc
Day 4 Inc
Day 5 Inc
Day 6 Restore with files from Day X, Y, Z.


You can actually set it to one. Then it keeps one complete (i.e. not interrupted) backup.

Usually you want to keep a history in case a file is deleted and you realize that, say, one week later. But it depends on the scenarious you want to recover from, of course.

As said. Every backup behaves like a full. So you can delete any file backup you want whenever you want and all other file backups will still be okay (you should not delete them manually, though).

Well ok. Thanks for this answers.

there*s one more point i need to know.

One big advantage of Incremental Backup is the Time needed for them.

An Incremental is set “on top” of the last inc backup to reduce BackUp time while having full file recovery if needed.
Wont UrBackUp need as long as for a Full backup if i only got one Inc at a time?

We BackUp via Network from Server to NAS.

Or is UrBackUp using the files from last Inc, simply copy the existing to ne new Inc and replaces the changed files Via Network?

hope my question is understandable cause my english is a bit rusty :wink:

Thanks in advance