OpenZFS – add disks to existing RAIDZ
I’m frustrated because this feature was mentioned by Schwartz when it was still in beta. I thought a new era of home computing was about to start. It didn’t, and instead we got The Cloud, which feels like decentralization but is in fact massive centralization (organizational, rather than geographical).<p>Some of us think people should be hosting stuff from home, accessible from their mobile devices. But the first and to me one of the biggest hurdles is managing storage. And that requires a storage appliance that is simpler than using a laptop, not requiring the skills of an IT professional.<p>Drobo tried to make a storage appliance, but once you got to the fine print it had the same set of problems that ZFS still does.<p>All professional storage solutions are built on an assumption of symmetry of hardware. I have n identical (except not the same batch?) drives which I will smear files out across.<p>Consumers will <i>never</i> have drive symmetry. That’s a huge expenditure that few can justify, or  much afford. My Synology didn’t like most of my old drives so by the time I had a working array I’d spent practically a laptop on it. For a weirdly shaped computer I couldn’t actually use directly. I’m a developer, I can afford it. None of my friends can. Mom definitely can’t.<p>A consumer solution needs to assume drive asymmetry. That day it is first plugged in, it will contain a couple new drives, and every hard drive the consumer can scrounge up from junk drawers - save two: their current backup drive and an extra copy. Once the array (with one open slot) is built and verified, then one of the backups can go into the array for additional space and speed.<p>From then on, the owner will likely buy one or two new drives every year, at whatever price point they’re willing to pay, and swap out the smallest or slowest drive in the array. Meaning the array will always contain 2-3 different generation of hard drives. Never the same speed and never the same capacity. And they expect that if a rebuild fails, some of their data will still be retrievable. Without a professional data recovery company.<p>which rules out all RAID levels except 0, which is nuts. An algorithm that can handle this scenario is consistent hashing. Weighted consistent hashing can handle disparate resources, by assigning more buckets to faster or larger machines. And it can grow and shrink (in a drive array, the two are sequential or simultaneous).<p>Small and old businesses begin to resemble consumer purchasing patterns. They can’t afford a shiny new array all at once. It’s scrounging and piecemeal. So this isn’t strictly about chasing consumers.<p>I thought ZFS was on a similar path, but the delays in sprouting these features make me wonder.