Do you still need to run a preclear if you have run a 4-pass badblocks?

Yes. Either run the preclear script, or add it to the array and UnRAID will preclear it for you.

Doesn't the unRAID preclear-like procedure require your array to be offline while it's running?

Doesn't the unRAID preclear-like procedure require your array to be offline while it's running?

yes, it does.  The array will be offline/not-usable for quite a few hours when adding a drive to an already established parity protected array.  (figure 5 to 8 hours or more of off-line time)

 

Also, it ONLY writes the blocks on the disks, it does nothing to read them to see if they are readable until after you first run a full parity check after assigning the drive.

Do you still need to run a preclear if you have run a 4-pass badblocks?

If a disk does not have a pre-clear signature, it will be cleared by unRAID. 

badblocks does not write the unRAID pre-clear signature to any disk.

 

The disk will have been exercised, but unRAID will zero again it if added to an existing parity-protected array.