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I heard you can expand a raidz if you add one with the exact same setting. So is it true that I can build a raid-2z now using 4 disks (so I have 2+2) and later on add another 4 disks so I have a raid-2z with 6+2? Or will this lead to 4+4? Is it even possible to have 3+1 now and add 4 drives so I have 6+2?

I ask this because I want to have 6+2 in the future but do not have enough money to buy all drives by now.

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up vote 1 down vote accepted

A RAID-Z group cannot be re-shaped to more or fewer drives after being created.

One option that would get you close to what you want would be creating the pool with one RAID-Z1 group with the existing 4 drives now, then adding another RAID-Z1 group to the pool with the 4 new drives later.

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but these would be two independent raid-systems or do I get something wrong here? – Schakal_No1 Feb 5 '12 at 9:23
You'll have two independent RAID-Z groups within the same storage pool. The new group will seamlessly supplement the old's capacity, but your redundancy will be weaker than a simple RAID-Z2; you'll be able to lose a disk from group A and a disk from group B without data loss, as opposed to two disks from anywhere. – Shane Madden Feb 5 '12 at 19:28

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