I'd like to install ubuntu server 20.04 with a few SSDs in a RAID1 for the boot/OS drive, and a handful more SSDs in RAID6 for storage, then finally have 2 hot spare SSDs which would be able to be auto-added into either RAID array in case of failure of any drive. I'm planning to have this machine put at a colocation data center, so hoping to be as redundant and hands off as possible.
Boot/OS RAID1: 3 drives
Storage RAID6: 8 drives
Spare: 2 drives
Using this I've been able to come close to doing this, and this is the guide I was thinking to use for my hot spares, but my problem is that I have different partitions on the boot drives than the storage drives because it has the boot partition, /, and swap. I have md0 as / and md1 as swap (both RAID1), then the entire drives as md2 for my RAID6. I tried to do LVM with the entire boot disk remainders, but when I would go into LVM during custom partitioning after making a single md0, the ubuntu installer would crash (all the lines were blank in LVM but I could select lines but then it would crash). So if a boot drive were to fail, it would need a drive to add to both md0 and md1 and hopefully be added as a new boot drive, and I don't think the hot spare has the ability to be formatted into the two separate MDs like that, or be added as boot.
Is it possible to somehow run ubuntu live on a usb stick and create an md0 RAID1 and md1 RAID6 of the entire disks I want, then go to the installer and select the md0 as a boot drive? I want to be sure that if a hot spare replaces one of the boot drives that it becomes a boot drive too.
My current plan is to simply leave the two extra drives just sitting in there, and then if a drive fails I would need to go and manually parition it and replace the failed drive in mdadm manually, but I'd love to have this be automated if possible.
