Differential Backup Size vs. Full Backup Size

radiowaves · 14 Oct 2017

My backup process is to manually do a full system backup followed by periodic differential backups until the size of the differential backup gets too big. My question is how big is too big? My thinking (and this is just a guess) is that when the differential backup is about 25% the size of the full backup, then it’s time for a new full backup. But again that’s just a guess. Is there an optimal percentage? I use the free version of Macrium Reflect 7.1 on a Windows 10 (1703) 64-bit Home PC.

RolandJS · 14 Oct 2017

Since I've not done differential backups, I'm going to follow this thread and learn alongside you from the experiences of others who have done such backups.

Steve C · 15 Oct 2017

radiowaves said:

My backup process is to manually do a full system backup followed by periodic differential backups until the size of the differential backup gets too big. My question is how big is too big? My thinking (and this is just a guess) is that when the differential backup is about 25% the size of the full backup, then it’s time for a new full backup. But again that’s just a guess. Is there an optimal percentage? I use the free version of Macrium Reflect 7.1 on a Windows 10 (1703) 64-bit Home PC.

There is no right answer. I schedule a full monthly backup and weekly differential backup. I also use File History for hourly backup of my user files.

cereberus · 15 Oct 2017

There is no correct answer but 25% seems reasonable. If you keep the differentials eventually, their total size wil exceed the original full hdd.

I tend to use diffs (or incs) as a temporary measure eg I want to try something, and just want ability to revert quickly just in case.

kronckew · 15 Oct 2017

if you like macrium, why not pay for the home version and use incrementals, they have to eat and feed their families too.

i do a weekly full on fri. night and incrementals the other 6 days, and have it set to keep two sets, each with a full and up to 6 incrementals, my full is about 54GB and incrementals vary around 1.6gb depending on how many changes i've made. restores can be done in around two minutes if the delta restore is active and changes are not major. i did a manual full on sat. due to the update to 1709 build 17017.1000.