Question about zpool remove vdev

[Borja Marcos]

Hi,

I have just noticed a nice new feature: the ability to remove a vdev from a pool.

I am considering to use it to fix a poorly made pool (sins of youth, created in 2012) which right now
has two raidz1 vdevs (yes, stupid!). I would like to recreate new vdevs with more redundance. 

Something like:

# zpool remove pool raidz1-0
# zpool add pool raidz2 [disks from the former first raidz vdev]
# zpool remove pool raidz1-1
# zpool add pool raidz2 [disks from the former second raidz vdev]

I have tried the memory estimation,

# zpool remove -n pool raidz1-0
Memory that will be used after removing raidz1-0: 711M

And now I wonder. Is this memory usage transient or permanent? 

If I add a new vdev after removing one, what happens? I guess there will be no 
automatic rebalancing. In that case I imagine making new copies of datasets
would be the way to do it. Right?


Thanks!




Borja.