Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

For 3DS games I use NDSTokyoTrim to remove useless data from the game files to make them smaller.

DreamCast, PS1 & PS2 games get compressed to chd with chdman.

GameCube and Wii are compressed to rvz with Dolphin.

PS3 I remove the PS3_UPDATE folder, 256MiB for each game adds up. I also use Gnarly Repacks for PS3 games since they have better compression than anything I've tried so far.

Switch games, I use nsz.

Then I use tar with zst on all of them, Nsz and rvz already use zst so theres no change but I just like to keep everything the same accross all of my roms and pc games.

Everything else, GB, NDS, SNES etc all get archived and compressed with tar and zst. For these I'll also use the --ultra -22 option since they're small enough files anyway so they don't take long to compress/decompress. If anyone knows any specific compression/trimming methods that are better than zst, I'd love to hear about them!

Copies of all the tar archives are kept on 2 separate drives and a copy of the games are on my PC in whatever the smallest format is that is compatible with their emulator.

I would have thought that the vast majority of people who download ROMs download them individually based off of their preference, not downloading the entirety of the PS1 or PS2 library.

To answer your question, it doesn't matter other than compression. Backups are backups.

My backup is seeding.

If anybody has a good option let me know. I tried using one drive to back up my entire lunchbox install (about 780GB) and Microsoft said nope. Apparently they give you 1 TB of storage but if you upload too much they cut you off. Pretty lame.

Whatever file format I use them in is also how I back them up, I backup my entire desktop's and laptop's data to an external hard drive and an online service provider. I'm sure a compressed format would be more space efficient but that would take much more time given my use case.

In the case of my laptop it runs Linux and the filesystem I use supports "transparent compression" (almost all contents of the drive are compressed with zstd), so I'm guessing any of the ROMs on there will have already been compressed as nuch as they can (but I'm not knowledgeable enough on the file format specs)

Send them to me! I have 30+ Tb of storage

If the emulator can't run games from archive files, then I store what I play unarchived, and what I don't play stays as archived as it was.

Unless they're small files, then I'd probably back then up extracted. But I haven't had a case where the files were small enough for me to store extracted but the emulator couldn't run from archives.

I have terrible but defined habits for my ROMs. I use the same folder structure for all of them.

./[platform]/[game]/[game].zip

./[platform]/[game]/[game].iso

./[platform]/[game]/saves/...

If it's a series, using Pokémon as an example, I also have:

./Pokemon/Backups/[game].zip

./Pokemon/[generation]/[game]/[game].iso

So it's not that good of a backup, mainly there in case the iso corrupts, but I think it's better than nothing.