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Suggested automatic cleanup settings for differential backup method?

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Differential backup method. Source PC drive is 238GB capacity but uses 90-110GB depending on how recently I cleaned the System Restore cache. The target is a 223GB spare SSD I had laying around. I am getting drive full all the time, and not sure how to configure the automatic cleanup settings as the phrasing and terminology is confusing me. Can anyone recommend best automatic cleanup settings? I don't need a month of backups all the time, I mainly use this as recovery in the event my NVME drive fails as I have heavy DRM on the PC and clean install of Windows would break hundreds of files.

 

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There can be lots of confusion around the topic of automatic cleanup which can be better understood if some basic concepts are known!

First:  automatic cleanup only works on complete(d) versions / version chains.  Do not expect individual elements of version chains to be cleaned up, such as incremental or differential files!

Second: automatic cleanup only runs after a new Full backup for the next version / version chain has been created successfully.  This means that there must be sufficient free space available on the storage drive / location to hold a new Full backup image file!

Third: counting of days does not start until after a new Full backup file has been created when using the option to ‘Delete versions / version chains older than X days.’  It does not start for the active backup version / version chain before that point!

Fourth: the simplest & easiest automatic cleanup option to use & understand is to ‘Store no more than X recent versions / version chains.’  The criteria here means that if you set X = 2, then when the X+1 (3rd) version / version chain is created successfully with a new Full backup file, then the oldest version / version chain will be deleted by automatic cleanup.

Example:

Incremental backup task, using Full plus 5 Incremental backups before next new Full backup.

Task scheduled to run daily with automatic cleanup set to ‘Store no more than 2 version chains.’

Day 1 – Full backup created.

Days 2 – 6 Incremental backups created.

Day 7 – Next new Full backup created. 

Days 8 – 12 Incremental backups created.

Day 13 – Next new Full backup created.  Automatic cleanup deletes files created on days 1 – 6.

If the same task used ‘Delete version chains older than 7 days’, then those 7 days wouldn’t start counting until day 7 for the first set of files (version chain 1) and not until day 13 for the second set etc.  So automatic cleanup wouldn’t delete the oldest chain until day 14 in the above example.