It seems NFSv3 didn't really fix the issue and ran into others (e.g., weird user IDs on remapping). I've gone back to NFSv4 and increased the number of NFS servers/processes from the default of 4 up to 5 to see if that helps.
@beatbox32 Everything looks good, including your mount. Did you remember to re-generate the gamelists from the RetroPie Skyscraper script? Scraping the data simply add it to the Skyscraper cache located at /home/pi/.skyscraper/cache (which is also a symbolic link if you installed Skyscraper from the RetroPie script). But you need to re-genereate the gamelists for it to create the necessary ES gamelist.xml files and artwork files in the /home/pi/.emulationstation/downloaded_media/ platform folders.
Remember to push space for each platform when generating the gamelists to select them.
EDIT: Skyscraper also checks if gamelist.xml is writable before it starts. It won't run unless it is.
Boom! Now it's working. Many thanks for the education on how the cache system works. I think I had a few missteps along the way where I was mounting the media folders as root and not the pi user, running into write issues initially. Once I resolved that, I apparently forgot to re-generate the gamelist.
The real answer is not that you are getting better performance. It's that you simply aren't as aware of how those heavy games are actually supposed to look like running at full speed so they look "good enough" to you when in reality, they are chugging, lagging, etc..
No that's not it, considering there are clear differences that can be visually perceived.
@Crush I can't think of any reason for that. Actually, a network storage would add some delay when loading data compared to a local storage.
Having such an immensely complex system like RetroPie and its underlying Linux OS makes comparisons very difficult, as long as not everyone has a freshly installed system from the same image with the same peripheral hardware and settings. Picking one prominent difference is not much more than a wild guess.
That said, which "heavy games" are we talking about exactly? And how do you compare your system's performance to those of others?
Thanks for that explanation, makes sense, I kinda wondered if maybe somehow it took of some of the load of handling the storage, but I'm guessing that's not possible then.
It's mainly Dreamcast/Atomiswave/Naomi games, where some get stuttering while i don't, most notably in Marvel vs. Capcom 2 on Naomi, whilst on Dreamcast it stutters for me as well.
"as long as not everyone has a freshly installed system from the same image with the same peripheral hardware and settings. Picking one prominent difference is not much more than a wild guess."
You've hit the nail on the head with that.
@construkt Nice. Well as far as I see it you can choose what ever NAS OS you want since a NAS primary goal is to serve files to clients such as computers on any network through file protocols such as SMB and NFS. It doesn't matter what OS the clients have or what NAS OS you decide to go with as long as both NAS OS and the clients OS supports the correct file protocols.
And as @mitu says it is better to set up a data redundancy environment with RAID. This is also known as mirroring. Lets say you have 2x 2 TB hard drives added to a RAID Mirroring setup, both of the drives will be in the same hard drive volume and they are connected together so if one drive fails you will not lose any data, however this setup will have the cost of making only half of the disk space available. So instead of 4 TB total disk space it will only be 2 TB total but you will be protected if any power cut happens in your home. I have tried this from experience and on my point of view I only needed to buy a new hard drive to match the other to rebuild the volume again.
@enderandrew This isn't necessarily the case because some USB 2.0 flash drives are a lot slower than what the USB 2.0 standard allows in my experience. With A USB 3.0 flash drive, you will likely see performance much closer to the maximum USB 2.0 is capable of on the Pi as they are built for speed. I bought a low-profile USB 3.0 drive for this reason and in my case, throughput did not disappoint.