In the "Define Retention Rules" section of a backup plan, there is a check box for "Create a Synthetic Full if possible" box. I have that check marked. When does the merging magic happen?

What does "if possible" mean? IOW, when would it not be possible to merge incrementals?

For the external X drive, I have "Incrementals" set at "keep 30 backups." Will the merging of incrementals happen on or about the 30th incremental backup? So far in drive X, I see the full backup (00) and sequential backups from 01 through 13. It looks like it hasn't begun to merge incrementals yet. Is this normal?

For the external drive Z, the "Incrementals" is set to "keep 10 backups." Looking at the Z drive, I see a full backup (00) modified on April 22. The next in that series is an incremental with the number 12, then an increment numbered 13. Both 12 and 13 have April 22 as the date modified. Is this normal? Has the merging already happened on that backup set and is that why increment numbers 01 thru 11 are missing? Full backups are supposed to run every Sunday. Why was the full backup modified today (Wednesday April 22)?

In the "Define Retention Rules" section, I'm not real clear what the two options mean:
Apply retention rules to matching backup sets in the target folder.
Apply retention rules to all backup sets in the target folder.
I read this page several times but still do not know what it means: http://knowledgebase.macrium.com/display/KNOW/_Retention+Rules

For the X drive, "Apply retention rules to matching backup sets in the target folder" is selected.
For the Z drive, "Apply retention rules to all backup sets in the target folder" is selected.

Hoping for more clarification on what these things mean and if it looks like my backups are running correctly. Thanks.
Posted April 22, 2015
Windows 7 64 bit, Macrium 6.0, build 567

Watison... I'll try and handle the first part of your question.

With your retention rules set to use INCREMENTALs only (in your scheduling), merging works as follows... the "Synthetic Full" option is only available if you have the # of Incrementals set to BACKUPS (not DAYs or WEEKs.  Currently... no real design limitation here, just implementation issues.  It could have been DAYs or WEEKs also).  If you have this set, when your Incremental # = # of INCS + 1, your Baseline (00-00) is merged with your oldest INC and the date of the Baseline is moved to the date of your previous oldest INC (makes sense since you're updating your Baseline to include changes in Oldest INC)... moving the Baseline along your timeline.  That oldest Incremental is now eliminated as it's no longer needed.  Each successive INC, at this point in time, will perform the same type of merger, basically moving your FULL+INC timeline forward.  This is INCREMENTAL FOREVER (IF).

If the "Synthetic Full" is unCHECKED, your original Baseline (00-00) will remain locked in time, and your oldest INC will merge with your second olderst INC.  This causes the INCs only to move forward in time and the Baseline will remain locked in time.  This is known as INCREMENTAL MERGE (IM).

When it says it will move the "Synthetic Baseline" if it can, it means if there are other types of images that are children of that Baseline, of course the Baseline cannot be moved.  Examples are a GFS schema where there may be DIFFs based on that full.  In the case of IF, there will be no other children of that original FULL so Baseline merges can occur accordingly.  If using a GFS scheme which may include FULLs, DIFFs and INCs... IM will occur with the Incrementals in that type of scheme also.

That KB article is saying (or trying to say) two things about what happens when you choose the option to Apply retention rules to matching backup sets in the target folder:
(1) the application of whatever retention rules you establish then depends on whether a backup set matches some specific backup definition parameters, and
(2) the matching process used differs depending on whether it is comparing (a) backup images of one or more partitions, or (b) file and folder backups.

If instead you choose the option to Apply retention rules to all backup sets in the target folder, then there is no matching to specific backup definition parameters, but the retention rules are applied to all backups of the same type (images backups or file and folder backups) located in that same destination folder. 

Hope that helps a little, although I have to admit that I found it somewhat confusing myself and difficult to clarify in a few words.


Regards, Richard V. ("Arvy")

Thanks for the replies Froggie and Richard.

I still do not understand, Richard, but maybe some day it will click in my head. Right now, my brain is pretty well frozen. Of the two options, which one should I choose?

Froggie, I did not realize that were two different processes: INCREMENTAL FOREVER (IF) & INCREMENTAL MERGE (IM). I thought the only merging that went on was when the box for "create a synthetic full if possible" is checked. Looks like I have more reading to do in the help pages. 
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Posted April 23, 2015
Windows 7 64 bit, Macrium 6.0, build 567

Apply retention rules to matching backup sets in the target folder would be the safer option in the circumstances.  Especially if you have defined more than a single backup task with the same destination, that option would be less likely to have unintended consequences.  Reflect's user interface can always be used for manual deletion of any other obsolete backup sets that are no longer wanted.


Regards, Richard V. ("Arvy")

Thanks, Richard. I think it's a little clearer now. It was the word "retention" that was throwing me off.

And I've since found this page, so now I know what GFS means:
http://knowledgebase.macrium.com/display/KNOW/_Backup_Plans_and_retention_rules