Disk Swap Query

[Duggie264]

BLUF: Can I replace a failed disk with a larger than parity disk (temporarily)?

Background:

I purchased three disks, one failed on testing, the other two were installed, subsequently one failed. The manufacturer, as part of the returns process has refunded the entire purchase amount to paypal for me, but I am now time limited in and have to return all three disks. All my disks (array and dual parity) are 14TB. I have two brand new 16TB disks.

My array now shows two disks missing (as expected) and is running "at risk"

 

Question
1. Will Unraid allow me to (temporarily) replace the missing 14TB drives with 16TB drives (I appreciate how parity works, but do not know A) if the extra two TB on the array disks will cause a parity fail, or B) if they will just be unprotected, or C) if Unraid will even allow the process). I have further 16TB drives on the way that will replace the parity drives in the event of B)

 

2. Am I correct in assuming that as I am missing two disks, I will be unable to swap a 14TB parity drive out for a 16TB (i.e. the swap-disable process?)

[itimpi]

1 hour ago, Duggie264 said:

or C) if Unraid will even allow the process).

Unraid will not allow the process.  You can never put a drive larger than either parity drive into the main array.

 

1 hour ago, Duggie264 said:

Am I correct in assuming that as I am missing two disks, I will be unable to swap a 14TB parity drive out for a 16TB (i.e. the swap-disable process?)

Assuming you mean Parity Swap then since you have dual parity (which means you can handle two simultaneous drive failures) you CAN use it to put a 16TB drive as parity and use the 14TB parity drive to replace a failed array drive.

 

[Duggie264]

Thanks @itimpi

 

So I already have dual parity, the issue now is I have dual (array) drive failures. 
 

I do have 2 16TB drives, but will I be able to swap out one of the Parity drives, when I already have two disks dead?
 

 

[itimpi]

5 minutes ago, Duggie264 said:

I do have 2 16TB drives, but will I be able to swap out one of the Parity drives, when I already have two disks dead?

Yes with dual parity.

 

Is one (or both) of the failed drives a parity drive or is it two data drives?   If the latter then you could run the Parity Swap procedure on two drives at once rather than doing them consecutively although you may prefer to do them one at a time.  

[Duggie264]

Yeah two dead data drives. 

[itimpi]

The Parity Swap procedure is specifically designed for the case where a data drive has failed and you want to put in a bigger parity drive and reuse the old parity drive to replace the failed one as a single procedure.  It work in two phases

• the contents of the old parity disk are copied to what will become the new parity disk.  During this phase the array is offline as there must be no changes to parity during this stage.
• when that completes the new parity disk is now used to rebuild the failed data drive onto the old parity drive.   The array is online during this phase albeit with reduced performance due to disk contention.

just thought I should check - are you actually sure the old array drives failed?   It is more common for drives to be disabled by Unraid (because a write failed) due to other factors such as cabling, power, etc than actual failures of a physical drive.   You never posted your system’s diagnostics zip file so we could check the SMART information for the drives.

[Duggie264]

Yeah I am positive - they were brand new drives and were clicking from the get go - one failed to even initialise, and by the time I realised both the other drives had mechanical issues, one had already successfully hounded the array, which subsequently died. 
 

Also happy with the parity swap procedure, just wasn’t sure how much more risk there would be swapping out a parity drive when there are already two failed data drives!

 

cheers for your assistance bud, much appreciated!

[itimpi]

5 minutes ago, Duggie264 said:

Also happy with the parity swap procedure, just wasn’t sure how much more risk there would be swapping out a parity drive when there are already two failed data drives!

Using the Parity Swap procedure the system does not start over-writing the contents of the old parity drive until it has successfully copied its contents to the new parity drive.  If for any reason you get a failure during this stage you still have the contents of the old parity drive intact for recovery purposes.  As long as the parity copy completes the new parity drive takes over the task of emulating the failed data drive while that rebuilds.

[Duggie264]

Awesome, thanks for the help and information!

 

best get swapping 😎