Does restore use both incrementals and differentials ?


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Clairvaux
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I have scheduled full images, differentials and incrementals. I'm wondering what files Macrium would pick up for restoring.

Suppose the last file is an incremental. Will it use all the incrementals + the full ? Or all the incrementals up to the last differential, then that differential, + the full ?

And if the last file is a differential, will it use that differential, + the full ?
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Edited 14 January 2021 8:39 PM by Clairvaux
dbminter
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Near as I understand it, with Incrementals, Reflect restores data from the Full and all Incrementals in the chain.  Even if data has changed/been removed, all Incrementals are "read" for changes.  So, technically, all Incrementals would be "used" in addition to the Full.  With Differentials, you're only using the Full and the one Differential.  So, if you restored an older Differential where there's a newer one, I would think you'd be restoring older data.


I believe Differential backups contain all changes made since the Full it's parented to.  So, let's say you have a Full with File A.  Then, you add File B and take a Differential.  Then, you add File C and take a 2nd Differential.  Restoring the 2nd Differential would restore all 3 files, but restoring the first Differential would only restore File A and B.

Clairvaux
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dbminter - 14 January 2021 8:50 PM
Near as I understand it, with Incrementals, Reflect restores data from the Full and all Incrementals in the chain.  Even if data has changed/been removed, all Incrementals are "read" for changes.  So, technically, all Incrementals would be "used" in addition to the Full.  With Differentials, you're only using the Full and the one Differential.  So, if you restored an older Differential where there's a newer one, I would think you'd be restoring older data.


I believe Differential backups contain all changes made since the Full it's parented to.  So, let's say you have a Full with File A.  Then, you add File B and take a Differential.  Then, you add File C and take a 2nd Differential.  Restoring the 2nd Differential would restore all 3 files, but restoring the first Differential would only restore File A and B.

Thank you. In fact, you raised one more question I wasn't aware of ! That is : if I select an old incremental or differential, will Macrium restore only up to that incremental or differential, or will it include the newer ones ? I believe, just as you do, that restore will only take into account the changes up to the file selected.

Anything else would be absurd. This should allow versioning : restoring a former state at a selected date.

But my question was different : does Macrium combine incrementals and differentials to restore ?

My schedule looks like this :

F
I, I, I, I, I, I
D
 I, I, I, I, I, I
D
I, I, I

Assuming I select that last incremental, will Macrium pick up only incrementals, plus the full, or will it pick up the last 3 incrementals, the last differential, and the full ?

The reason I'm asking is, I'm assuming that incrementals are more risky, since only one of them getting corrupted breaks the set.
So I'm tempted to trigger differentials more often, or even at the same date, in order to be safer.
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To your new question, what I think happens is when you select an Incremental, all Incrementals in the chain are displayed in the Restore window.  But, the one you selected will be highlighted for restoring, but you could select a newer one after that.  So, I would guess if you choose an Incremental earlier on in the chain, then the changes in the Incrementals after the one you selected would be ignored.


To your last question, the way I understand it is Differentials are ignored in Incremental chains.  However, I haven't used Differentials in years, preferring Incrementals.  Actually, I prefer using Fulls except for daily backup changes after the morning Full, where I use Incrementals before installing new software or updates or make system changes.

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Your assumptions are correct.  The RESTORE operation will only restore up to the time point you have selected.

During any restore operation, REFLECT will use what's minimally necessary to get you, accurately, to your selected time point.  It doesn't use everything, just what's required to get you there... the most recent FULL, the most recent DIFF and the most recent INCs using whatever's available.

Edited 14 January 2021 11:26 PM by Froggie
jphughan
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Restores use the selected backup and any previous backup in the chain leading back to the Full.  If you have a set consisting of a Full, some Incs, and a Diff, and the latest backup is a Diff, then restoring that backup will only require that Diff and the parent Full, because those Incs aren't actually in the chain leading back to the Full, even if they're part of the backup set.  A Diff is always a direct child of a Full.  But a restore would never use backups created AFTER the one you're choosing to restore.

It's also worth noting that restoring from an Incremental does NOT require you to first run a restore for the Full, then the Diff (if one exists between the Full and Incs), and then individual restores for each Inc from oldest to newest.  You just choose the backup you want to restore, and Reflect will pull all data that it needs from any backups in the set in order to run that restore as a single operation.  Sorry if that sounds obvious, but I've come across several users in this forum who did not realize that was possible.  They believed they had to run a multi-restore process in order to restore an Inc.

Clairvaux
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Froggie - 14 January 2021 11:24 PM

During any restore operation, REFLECT will use what's minimally necessary to get you, accurately, to your selected time point.  It doesn't use everything, just what's required to get you there... the most recent FULL, the most recent DIFF and the most recent INCs using whatever's available.

Just to confirm I understood correctly, because that was my main point of ignorance, really.

Suppose my actual set looks like this :

Full - Inc 1, Inc 2, Inc 3 - Diff 1 - Inc 4

And I want to restore the last available state, corresponding to Inc 4.

Do I understand correctly that Macrium will use Inc 4, Diff 1 and Full, and ignore Inc 1, Inc 2 and Inc 3, which it does not need to achieve the job ?

jphughan
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Yes, and you would even have the option of deleting Incs 1-3, and you would still be able to restore Inc 4.

Clairvaux
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jphughan - 15 January 2021 2:45 AM
Yes, and you would even have the option of deleting Incs 1-3, and you would still be able to restore Inc 4.

Very helpful information. Thank you all for your assistance. 
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