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How should I go about adding 3 larger drives to my array?


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I've got an array with various drives. Parities are currently 4TB, so the max drive size is 4TB, but I've just bought 3 8TB drives, 2 of which will be parity after preclearing.


The two 4TB parity drives will become data drives, and ideally one of them will actually replace a 1TB drive I have.


So this is a whole lot to do! I'm trying to reduce the number of rebuild operations as much as possible. As I understand it, you can't add new drives at the same time as rebuilding another drive, which makes perfect sense, but that means the "standard" way to do this would be to swap out BOTH parities at once, rebuild parity, then add the 3rd 8TB and one old 4TB parity as data drives, rebuild parity, then rebuild the 1TB drive on the 4TB drive. That gives me a total of 3 rebuild operations just to add 3 drives! ?

Now, the 1TB is still fine, I'm just running out of license slots (not to mention physical slots) and it slows down parity checks. But is there any way I can maybe, remove parity protection, copy the 1TB data onto a 4TB drive (or really just somewhere else in the array), add the drives for data, then finally throw the parities in for a total of 1 rebuild operation?

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You mention running out of license slots, so I'm a little fuzzy on what drives are actually going where.

Could you list current and intended in a condensed format like this?


P1 -4TB

P2- 4TB

D1-4TB - 3.9TB Used

D2-4TB - 3.5TB Used

D3-1TB - 0.9TB Used






D3-Old P1 with 0.9TB


etc, etc.


It would help me (and others) to visualize where you are and where you what to go.


Also important is knowing the state of your backups and your tolerance for risk. Generally the more risk you are willing to take the faster we can get it done, however you have 2 parity drives, so I'm guessing your risk tolerance is pretty low, so it might be better to take it slow, unless your risk tolerance is extremely low and you have dual parity and full backup in 2 locations, in which case, damn the torpedoes full speed ahead.


Any time you are about to do wholesale drive rearrangement your data is at risk, so do you have clean smart reports and a 0 error parity check in the last few days?


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P1 - 4TB

P2 - 4TB

D1 - 4TB

D2 - 4TB

D3 - 1TB

D4 - 3TB

D5 - 4TB

D6 - 4TB

Cache - 250GB



P1 - 8TB

P2 - 8TB

D1 - 4TB

D2 - 4TB

D3 - 4TB (previously P1)

D4 - 3TB

D5 - 4TB

D6 - 4TB

D7 - 8TB

D9 - 4TB (previously P2

Cache - 250GB



Funny you mention my risk tolerance -- I actually have a pretty high risk tolerance for most of this data, the only reason I have dual parity is because I use the cheapest drives I can, and some are just drives I had lying around, or shucked out of external drives I've already used for a year. I just like the extra durability. I know I can do this slowly with high durability, but doing it slowly means many rebuilds, which also increases he likelihood of a failure overall, though I guess likelihood is very low.

Biggest thing is I'm skeptical of reliability of doing it while the server is being used -- I know it slows down operations significantly to use it while rebuilding, but I'd be concerned it actually increases likelihood of failure, where a single rebuild operation overnight wouldn't have those issues.

As for SMART reports and parity -- 2 drives have UDMA CRC errors, but they haven't changed in many months and reboots/parity checks I guess they don't disappear when you resolve them (as it's often just a bad SATA connection). Parity will be run tonight to ensure everything's up to snuff, as the 8TB's go through a preclear cycle.

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You missed the part about free space, what I was getting at was if you have enough space to empty that 1TB, you can do the whole thing in 1 operation.


IF the 1TB can be removed instead of rebuilt, then you can just do a new config without saving any slot assignments, and assign everything as you have laid out in your desired end result. You will be running at risk of drive failure until the parity build is completed and checked successfully, but if you have a clean parity check before you start, the risk should be fairly low.

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Ah! I didn't think of it like that! I do have quite a bit of free space, offloading that 1TB is no problem at all.


Will the 4TB drives that used to be parity come up as empty?

The risk of failure during parity build is surely no more than the risk of failure during parity CHECK, which I have no problem doing monthly, and often more frequently even than that.

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42 minutes ago, drumstyx said:

Will the 4TB drives that used to be parity come up as empty?

Sort of, not quite, but yes. They are full of individually meaningless 1's and 0's, so they will show up as unformatted when you start the array. Just be sure they are the ONLY drives showing unformatted, since the format command in unraid doesn't discriminate and will format ALL unmountable drives when you select it. If one of your currently in use drives happens to not mount for some reason, you don't want to accidentally format it as well as your ex-parity drives.


Just double check that the serial numbers of all unmountable drives to be sure it's just the old parity drives before you select format.

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I'd remove parity 2.


Mount it as a UD, the format it as XFS or BTRFS as per preference.


Copy the contents of disk3 to the UD.


Then do a "new config" and set to "Desired" config in your post above, and rebuild both parities.


Personally, before starting I'd preclear the 3 8T drives to make sure they are good.



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