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Cc: Dan Langille <dan@langille.org>
Subject: Re: Using GTP and glabel for ZFS arrays
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> So... the smaller size won't mess things up...
If by smaller size you mean smaller size of existing
drives/partitions, then growing zpools by replacing smaller vdevs
with larger ones is supported and works. What isn't supported is
basically everything else:
- you can't change number of raid columns (add/remove vdevs from raid)
- you can't change number of parity columns (raidz1->2 or 3)
- you can't change vdevs to smaller ones, even if pool's free space
would permit that.

Good news is these features are planned/being worked on.

If you can attach more drives to your system without disconnecting
existing drives, then you can grow your pool pretty much risk-free.