I'm assuming you mean vdevs — you can resize zvols (virtual block devices) just fine.
(and you can even grow disk-type vdevs, though they'll be somewhat unbalanced)
Re:Things you can do with ZFS [video]
by throwaway7767 on Thursday October 08, 2015 @08:03AM
(#10352119)
Yeah, sorry, edited. It's mainly the ability to resize RAIDZ or RAIDZ2 zdevs that would be really helpful.
Re:Things you can do with ZFS [video]
by Scramblejams on Thursday October 08, 2015 @11:09AM
(#10353228)
Me too. I've added so many drives in onesies and twosies to so many MD RAID5/6 arrays over the years that I simply can't confidently deploy ZFS for that case.
md RAID will require a lengthy reshape. BTRFS supports adding a new drive, reshape (balance) is optional.
Re:Things you can do with ZFS [video]
by throwaway7767 on Thursday October 08, 2015 @12:15PM
(#10353703)
> md RAID will require a lengthy reshape
Array reshapes are rare, and it'll only use idle IO bandwidth anyway. Redundancy is guaranteed during the whole process. So I don't see this as a problem.
> BTRFS supports adding a new drive, reshape (balance) is optional
Thanks for pointing this out. I didn't know btrfs supported array reshapes. I'm waiting for it to mature (RAID5/6 was only added in 3.19, for example) but I expect I'll switch over at some point, probably at the point it's considered "boring" (exactly the experience I want from my filesystems).
Also, if you add zdevs later, you will never get full performance again as the striping will be off (putting more writes on the zdevs with more free space), and there's no 'rebalance' kind of thing (I've seen some scripts that just move stuff around, but I've never seen any evidence that they work, and I really doubt that they do based on my understanding of zdev allocation).