This article discusses the common reasons why the Disk Space Management (DSM) options in Macrium Reflect may not work as expected.

1. Setting the 'Default' options does not change existing backup definitions
2. Setting the purge to run 'Before the backup' doesn't include the the current backup set in the calculation
3. Only similar backup or image types are included in the purge
4. Severely corrupt files will not be purged
5. Only full and linked incremental/differential files are deleted.

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1. Setting the 'Default' options does not change existing backup definitions

Setting the default options only changes the setting for new backup definitions created after the changes to the defaults. The default option can be changed by taking the 'Other Tasks' > 'Edit Defaults' menu.

To apply DSM setting to an existing definition right click in the file and select 'Advanced Properties'

Note: Check the log for the Disk Space Management line as shown below. If there's no DSM line then it isn't set in the backup!

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2. Setting the purge to run 'Before the backup' doesn't include the the current backup set in the calculation

A common mistake is to assume that if you select to retain a maximum of 2 image sets before the backup is run that there will only ever be a maximum of 2 image sets in the folder. This is not correct.  If you are running DSM before the backup then the current backup set isn't included in the calculation. For example, if you only have room for a single full image then you will need to delete all files before running the current backup, therefore, you need to set the DSM option to retain '0' full backups and to run 'Before the backup'.

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3. Only similar backup or image types are included in the purge

The DSM purge will only consider similar backup types for inclusion in the purge process. Therefore, if you have a folder with a mixture of File and Folder and Image backups, then the purge settings for an Image backup will not consider the existing File and Folder backups when deciding which files to delete.

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4. Severely corrupt files will not be purged

Files that are so badly corrupt that they cannot be opened by Macrium Reflect will not be deleted. The purge process needs to examine the contents of the files to determine whether the files are eligible for purging. If a file cannot be accessed then it will not be considered.

To check whether severely corrupt files exist click the 'Restore' tab and click the 'View' Load Errors' link 

Severely corrupt files are shown in Windows notepad.

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5. Only full and linked incremental/differential files are deleted.

Individual incremental and differential files are not considered when purging. These files are always linked to a full backup in a set. For example, if you have a full with 10 incremental backups or images then the entire backup set will be deleted when the full backup meets the purge criteria.

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