> ext4 online resize works by invoking resize2fs. That's resizing the filesystem not the pool (eg `mdadm --grow`). You're also missing the point about what I s

> ext4 online resize works by invoking resize2fs. That's resizing the filesystem not the pool (eg `mdadm --grow`). You're also missing the point about what I said. To run those commands you must first `umount` to pool. Hence it being an offline job. > QNAP and Synology don't do magic. They deploy mdadm, LVM and ext4 or btrfs (though btrfs only in single drive mode, they use LVM and mdadm to span the volume for btrfs). That's completely irrelevant to the point I was making. How many home users do you know who configure their own home raids using LVM and mdadm? > Reread what I wrote, I mentioned adding 2x2TB not 1x2TB. You actually said neither. You said, and I quote, "2TB" (ie without any accumulation prefix). > Still having redundancy is exactly the point. The resulting array in the example would span 6x1TB and 2x1TB in RAID5, giving me a single drive for parity in each span and resulting in an effective RAID5 for the entire RAID. I can loose any drive in that 4x1+2x2TB array without loosing data You can actually do that in ZFS. In fact what you've just described were is the exact solution that you called "unacceptable" in ZFS! > And it does that online without having to reboot or even halt any ongoing file operations. The volume will simply increase in size once it has finished formatting the new drive and integrated it into the array. Indeed. Lots of commercial tools do support that. I thought we were comparing ext4, LVM and mdadm to ZFS though? I'm guessing you just glossed other my post where I said you were flip-flopping all over the place? It's easy to pick any specific tool ("tool a")and compare it to a thousand other tools and argue that "tool a" is crap because it doesn't work as well as tool b, c and d in very specific edge cases but all you're doing is trying to win an argument via death from a thousand papercuts rather than forming a sane basis for analysis. To be honest I think it's probably best we give up on this discourse because your points are all over the place. This feels very much like you've got an axe to grind and no practical experience to back up your prejudices.