In previous posts I have explained how having dedicated filegroups for user data can improve our RTO by, in case of disaster, recovering critical data first and then the rest.
The thing is when you deal with databases which were not created this way, you need to move the data from one filegroup to another before you can apply this kind of techniques.
Here is where this post can show you one of the gotchas you can find during this process.
Read on for a demo of this.