[bestham]

I have run ZFS at home since 2011 and migrated to larger drives one time: from 6x3TB to 6x4TB. The only downside is that the slabs are smaller compared to a native 6x4TB array.

[tscs37]

That's not the problem here.

The problem is having a 6x3TB pool and turning it into a 7x3TB pool, which is arguably much much cheaper than buying 6x4TB.