Building engine sudden spike in disk capacity

I noticed something strange today. I currently have 20 gigs free on my drive. I start a build and it immediately jumps to 0 gigs free and the compiler fails. I kill the build and it goes back to 20 gigs free.

I have my windows explorer open, and tried refreshing constantly to see the disk free size drop from 20 gigs to 0, and back in a super short amount of time.

I’ve never seen anything like this, is this normal? How can a disk fill up that quickly anyway? I guess my PC is just that crazy fast at disk writes?

I actually just got some new SSDs during black friday sales and am about to fix my low disk space issue, but this was definitely an odd thing to encounter. I’ve previously had no issue working with only 20 gigs free before while building Unreal.

This might be the page file growing for virtual memory.
You might want to turn off page file, and/or limit it to a small fixed size, rather than “let windows manage it.”
Also, more RAM in the system will likely help.

I have 64 GB of RAM too. It probably is something to do with Virtual Memory.