Preclear - Does it Remember?

[Rikumo1978]

Hello,

 

I apologize if this was asked before, I couldn’t find it so here goes.

 

Im wondering if I have a spare disk right, I connect it, start the array, and run Preclear on it. Then I disconnect it, either from the Sata, or take it out altogether, and set it aside for a later date if I need to replace a failing disk. If I re-connect it and start up the array, will UNRAID remember that it’s already ran Preclear on it? Or will I need to re-do it because I disconnected it? 
 

Please advise. Thank you. 

[JonathanM]

IF no writes happen, it will be detected as precleared.

 

That means attaching it to any other machine is likely to invalidate it.

 

However, there is no need for a REPLACEMENT disk to be clear, because it will be overwritten with all the parity emulated bits that were on the drive it is replacing. The only time preclear saves time is when you are ADDING an additional disk slot to a parity protected array.

 

Preclear just happens to also be a pretty good stress test to hopefully weed out DOA drives, so your process of preclearing it before shelving it for a rainy day is a good practice even if it's not technically needed for a replacement process.