I work with extremely large PSB files (~20-100 GB). Supercharged Windows 10 machine built for this purpose alone, that includes:
NIVIDIA Quadro P4000 (8 GB RAM)
128 GB RAM
1 TB OS Drive
14 TB Data Drive
4 TB Data Drive
2 TB, RAID 0 scratch disk
Previous project file was 50 GB and used approximately 500 GB of my scratch disk. Current project file is now reduced to 22 GB. After upgrade to PS 2020, I had to add 2 additional scratch disk options and TEMP files are now eating 4 TB and counting! It's creating anywhere from 3 to 8 new 64 GB Temp files every minute when using the program!
After spending 1 hour on tech support, I was told this is normal, expected behavior; to use 10+ times as much scratch disk space as Photoshop 2019!
Version 21.0.2 should be available to you shortly and contains our changes to correct the excessive scratch space usage issues with Legacy Compositing disabled.
I'd like to know whether the changes have resolved all the issues listed here. If you still have document size issues with 21.0.2, please follow up by eMailing me at carboni @ adobe . com (no spaces). I want to make sure we get this right.