What is this folder for?

Hi I was just wondering what the dev_hdd0 folder was all about. I've only got around 10 games and the folder is not far from 20GB!
What's the reason for this?

There is a folder for GTA5 that seems to mimic the discs. Does the emulator mimic the PS3 by installing the games to it's internal drive for speed? It's just that if you had a large collection, this folder would be massive!

Is this something that may change in future versions of RPCS3?

Thanks for your time

It's the folder where user content is stored. It contains data like PSN games (dev_hdd0/game/GAMEID), DLCs, updates or game data (only for disc-based games). In dev_hdd0/home/*user_id* contains information about the installed trophies, user's savedata or RAP licenses (required for PSN games and DLCs).

Usually disc-based games install content into the hard disk to reduce loading times in the real hardware. However, in an emulator, it's almost useless, since a lot of PC hard drives are faster than the PS3 stock hard drive. IIRC, Gran Turismo 5 allows you to stop the installation of game data.

Thanks for your reply.
I see, so are you saying this feature is redundant for RPCS3?
Will there be a time when this data cache will no longer be used?

It's redundant for RPCS3 because you already have the game on the same drive (or on a drive with similar or better speed) where you're going to play it.
It's used on PS3 because the BD drive is very slow so games install themselves to the HDD.

Few games let you choose whether to install or not, but most don't, so you're forced to install them to the virtual hdd.