Does size of Time Machine backups increase after changing from HDD to SSD on a Macbook Pro? I upgraded to an SSD earlier this year, and the experience has been great!

I use Time Machine for backup on a weekly basis on to an external hard drive and have noticed that the size of the backups have grown ~5X. Earlier, with a hard drive, the size of the backup was ~10GB, and now, the backup size is ~50GB.

I suspect this has something to do with the way SSDs work, specifically something about SSDs having to rewrite huge sections of memory even if only a part of the section needs to be changed. 

Has anyone had a similar experience?

Hardware: I am using Micron's Crucial BX100 SSD on an early 2011 MBP running OS X El Capitan (Version 10.11.6)
I suspect this has something to do with the way SSDs work, specifically something about SSDs having to rewrite huge sections of memory even if only a part of the section needs to be changed.


This happens at the storage and controller level - it is completely transparent to the operating system.

You have already found the main cause, but one thing you didn't notice was that the day after you changed your drive, Time Machine did a complete backup from the beginning. TM noticed a new device ID on the drive and made a new backup. It is possible to join backups IF you do it before the first run after the drive change, but it involves some tinkering in the Terminal.