Fault tolerance is achieved by duplicating data over several devices.
Using either Linux MD-RAID or ZFS, up to 7 redundant disks are supported for the root filesystem.
Optionally, all partitions could benefit from Full Disk Encryption.
POOL_TOPOLOGY configuration directives allows several setups.
POOL_TOPOLOGY directive supports all Linux MD-RAID setups, read Configuration file format / Multiple ext4 partitons on linux md raid array.
ZFS tag, then
POOL_TOPOLOGY implements ZFS
zpool vocabulary, read Configuration file format / Zfs volume management.