Ever since I replaced two drives in my four drive NAS, a Synology DS408, I wanted to do something about the RAID partitions of that NAS. I had replaced the two drives because I kept having data issues with them. This in the end turned out to be an issue with the cables. Synology was nice enough to quickly send me new cables, but by that time I had already replaced two of the four 1 terabyte drives by 2 terabyte drives.
After replacing the two drives the RAID volume had been rebuilt as it would have had I filled the empty slots with one terabyte drives. So two terabytes of space was now unallocated and therefore wasted. I was considering putting a RAID 1 volume on the two empty spaces, but nowhere could I find an option to add another volume.
I read up on how Synology’s software running on the NAS works and it seems the only way to use all of the space on all drives if you have drives of different sizes, is using Synology’s Hybrid RAID technology. Pretty soon I found out there are some limitations. SHR doesn’t allow for different types of RAID volumes next to each other. So I could use all the space on all disks, but only if I used a single RAID 5 volume. RAID 5 only tolerates one faulty disk and I didn’t get a four drive NAS to have a system that could only handle a single drive crash at a time.
So now I’m back to RAID 6 with four one terabyte RAID partitions giving me about 1.8 terabyte of storage. Oh well, better safe up for two more two terabyte drives.