Hello. I’m completely new to TrueNAS. I will be purchasing a case with room for 8 drives. I don’t expect that I will be purchasing 8 large spinning drives in the beginning due to their cost. So, I’m thinking along the lines of purchasing the minimum number of drives for a RAIDZ2 configuration and then adding drives over time. What is the minimum number of drives for a TrueNAS RAIDZ2 configuration? Would it be difficult to add drives over time to a TrueNAS RAIDZ2 configuration? Thank you.
4 drives.
Raidz expansion is not difficult, but it has some minor drawbacks compared to creating a vdev at the right width (wrong reporting of free space, and sub-optimal space use).
@etorix Thank you for the reply. I guess I should go ahead and purchase all 8 drives then and configure them all at the same time so I don’t have any issues.
Now I’m wondering if a drive goes bad and I go to replace it with a larger drive size, what might occur?
You will not get the benefit of the larger capacity until all drives in the VDEV have been replaced. Other than that, nothing bad will happen.
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@neofusion Thanks for that info. When a drive does go bad, typically a couple years down the road, and you go back to find the exact drive you used in your initial build, you can’t find it. So you end up buying something comparable, likely a little larger, and replace the bad drive.
If you don’t get the benefit of the larger capacity, for instance replacing the bad drive with one that’s a little larger, until all of the drives in the VDEV have been replaced, do you at least get the capacity of the initial size? For example, you initially purchase 8, 6TB drives, and 1 goes bad. You replace the bad drive with an 8TB drive. Will TrueNAS just use this new 8TB drive as 6TBs? I hope that makes sense.
Correct, TrueNAS will partition the new drive and will create one to match the existing drives’ partition size. The leftover 2TB will be unused.
@neofusion Great knowledge. Thank you. I appreciate your time.
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Not quite “match” the existing drives’ partition sizes. This would prevent pool capacity expansion in the future.
What it does (since the bugfix) is it will partition the entire drive, minus a 2GB “buffer”. Only 6TB of the 8TB partition will be usable in the current vdev, but the remaining space will be usable when all members of the vdev are replaced with larger capacities.
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@winnielinnie Thanks for that info. I appreciate your time.