| Yes, you can put drives of similar sizes in raid groups ("vdevs") together and then stripe together dissimilar groups. You can also put them all together in one big group, but in that case the group will act as though all the drives are the size of the smallest one and waste the rest of the space. Example disks: * 2x 500GB * 4x 1TB Example of first option: * Mirror of 500GB: 500GB * RAID-Z of 1TB: 3TB * Total Usable Storage: 3.5TB * Total Overhead (Redundancy): 1.5TB * Pool fails if any two drives of the same size are lost Example of second option: * RAID-Z1 of all: 2.5TB (Effectively RAID-Z1 of 6x500TB) * Total Usable Storage: 2.5TB * Total Overhead (Redundancy): 500TB * Total Wasted: 2TB * Pool fails if any two drives are lost Terminology/facts in case any reader doesn't know: * A mirror is what you'd think, basically RAID 1. * A RAID-Z(1) is a RAID group with a single disk worth of
redundancy, like RAID 5. * RAID-Z2 and RAID-Z3 are two- and three-disk redundancy
groups respectively. * ZFS can stripe together any number of similar or dissimilar groups of drives, but if any one such group is lost the entire pool is corrupted. Edited for formatting Edit Edit: These behaviors are due to ZFS, not choices made by the FreeNAS developers. |