I recently got a few (5) hard drives to turn my home server into a NAS with trueNAS scale and my idea is to have 4 usable and 1 for redundancy, my question is… How does RAID work, like what is RAID 0, RAID 5, software RAID etc, and does any of that even matter for my use case?
You have a 5GB file:
RAID 0: Each of your 5 disks stores 1GB of that data in alternating chunks (e.g. the first disk has bytes 1, 6, 11, second disk has 2, 7, 12, etc), occupying a total of 5GB. When you want to access it all disks read in parallel so you get 5x the speed of a single disk. However if one of the disks goes away you lose the entire file.
RAID 1: The file is stored entirely on two disks, occupying 10GB, giving a read speed of 2x, and if any single disk fails you still have your entire data.
RAID 5: Split the file in only 3 chunks similar to above, call them A, B and C, disk 1 has AB, disk 2 has BC, disk 3 has AC, the other two disks have nothing. This occupies a total of 10GB, it’s read at most st 3x the speed of a single disk, but if any single one of the 5 disks fails you still have all of your file available. However if 2 disks fail you might incur in data loss.
That’s a rough idea and not entirely accurate, but it’s a good representation to understand how they work on a high level.
Better explanation of raid 5:
You have 5GB of data and 5 disks. You split your data into 4 parts and split one on each disk. Then disk 5 remembers if there is an odd or even number of 1s on the other disks. So whichever disk fails you can count if it was odd or even. So you loose 1 disk but keep full capacity of the other disks. No doubling like suggested before
