I only have a 120gb SanDisk ssd and i need more storage. I started looking into RAID but from what i understand, RAID will not increase storage, just performance and/or reliability. I want to have multiple disks, but i want them to be read by the os as one disk so i have more storage without having to go into /data/media/storage ect. (i use linux mint). is there a way to do this? will it also increase performance or reliability?
You can do what you want with raid. You can set up a raid 5 system with 3(or more) disks, and have more than 1 drive of total space, and redundancy in case 1 drive fails, and can increase performance. The system will see 1 volume spread out over several disks.
If you have 3 120GB drives, you'll end up with about 240GB of usable space in a raid 5 configuration. Adding more drives will increase usable space.