Thanks for all the helpful replies!
Especially for the tip about raid 10, I never used it before and didn’t know that’s what raid 10 was. It makes sense: 1+0 so well done to whoever designated the number.
I hadn’t realised that btrfs was “pretty dead”. I know Red Hat deprecated it but I’d thought it was still a decent choice for cases like this.
I can see that both btrfs and ZFS support raid10 with checksums so my next questions is, should I use ZFS without in-kernel support or kernel supported btrfs? ZFS looks more mature but what happens if people stop development to make it work with whatever kernel is in use in 5 years?
And actually I’ve just answered my own question in my mind while writing this response. I might as well include my question and own answer: My point was going to be that although I could move the data to a different filesystem before upgrading to a kernel that didn’t’ support it, I’d need enough free space to copy all my files from the 4 drives (or however many I have by then).
But, as I was typing I realised that I’m doing mirrored striping so I already have that space. I could scrub the filesystem, I then known that the data on both of the mirrors is fine, format 2 of the disks to a different filesystem and copy the data across then add mirroring on the new filesystem. So as long as s future filesystem supports moving from raid0 to raid10 this will never be an issue in my situation.
I just tried setting this up with ZFS and it was worryingly simple. I definitely didn’t feel like I earned it
If I’m only using them for storage is this still a consideration? I haven’t used a HDD as a boot drive since I got my first SSD in 2007 and don’t think it’ll ever be something I need. I have several spare 64gb and 128gb ssds that are too small for me to find a decent use for that I can use for a boot device if I ever want to play around with different OSs.