On Sat, Dec 6, 2014 at 9:40 PM, Tim Hamilton <hamilton.tim@gmail.com> wrote:
Given my plan is to increase capacity by adding, rather than replacing, drives it looks like an mdadm managed raid 5/6 pool might be the better option.
My method was to decide on my fully populated capacity: 9 drives, and then just source old drives to make that happen. So my initial raidz array was 3 x raidz1 vdevs, each with 3 drives. In my initial state these were 500gb drives I had lying around, or sourced for very cheap. 4 of them were even PATA. I was then able to replace them with larger drives, 3 at a time. 2TB drives were best cost/capacity at one point, so I replaced 3 drives with those. Next time I needed a storage boost, I did it again with 3 more of the 500GB drives (now free of PATA). Most recently, I replaced the last bunch with 4TB drives. Next time a jump is needed, 3x2TB drives will move to 4TB. As long as you can source some cheap old (but still relatively reliable) drives, you can still use ZFS in the same way as mdadm. cheers, / Brett