I’m looking to start a nas and have three 8TB drives. I would like to expand pretty quickly (in months not years) to about 36TB total space. Wit the new expansion features in TN Scale, can i start the three disks in a RaidZ2? I don’t want to start in a Raidz1 because after the expansion i want the extra protection of RaidZ2.
Yes you can. I don’t think that any existing data is restriped to the extra disks though. There might be other downsides, but I think that is the big one.
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The GUI may not let you make a three wide Z2.
GUI space reporting if off, you have to use CLI to get accurate numbers after Raid-Z expansion
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Now that I’m thinking more about it. I might just do a Raidz1 with the 3 disks and start with 16TB. Then buy three more and mirror it like a Raid 10. Then I can expand from there?
Raid-Z1 isn’t recommended with large drives due to how long it takes to resilver and you have no more drive redundancy while that is going on.
There are ways to create the Raid-Z2. You have to use CLI or maybe your create it with three real disks and a sparse file for the fourth drive and then remove the fourth drive, leaving you with a four wide, degraded Raid-Z2. I am hoping someone familiar with the process will post. I couldn’t find a post explaining it quickly.
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The advantage of creating a degraded 4 disk RAID-Z2 over a 3 disk RAID-Z1, is of course whence you replace the missing disk, you get 2 disks worth of parity. Note that I don’t think RAID-Zx expansion will work with a degraded pool. The missing disk must be replaced before adding another data column.
In the mean time, you get about 16TB of storage, (well, really less because 8TB is not really 8TB and their is overhead…). These 3 disks in RAID-Z2 would have the equivalent storage of 2 data and 1 parity to begin with, just like a 3 disk RAID-Z1.
As for how to do it, this is tricky. I KNOW I can do it, but trying to walk someone else through it remotely, well, that is beyond my skill set. However, it may be possible to group source the procedure.
For example, creating a temporary pool using the 3 disks in a RAID-Z1 from the GUI, will likely partition the drives correctly. Then, destroy the temporary pool and use these partitions for the degraded RAID-Z2 pool.
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