So, I am putting together an Unraid backup system.  I cannot afford new drives, but acquired 4 WD 4000 Re drives.  Kinda high hours, out of a datacenter environment.  I have been running them through preclear, so far 1 passed and 2 have 2 pending sectors each.  

 

My question... I intend to set the passed drive up as parity and use the others as data drives.  My main server has good drives in it, so not so critical here.  I see loads of people installing used drives, I assume most used drives do not pass a preclear.  What do you guys do in that case, use them or lose them?

If a drive will not pass a Preclear then you should not use the drive.   If a drive fails during normal use of the array then Unraid requires all the remaining drives to be able to read error free to recover the contents if a failed drives.  
 

Pending sectors are never a good sign although it is possible that they can get reset to 0 during the Preclear process.

 

as an alternative to pre-clear you can run the extended SMART test on the drives.    If this fails a drive should not be used.

That is what I figured... good to know. 

14 hours ago, mattw said:

I assume most used drives do not pass a preclear. 

That is a bad assumption. A preclear isn't all that special, it just confirms that all sectors of the drive can be written to and read from without error. If a drive doesn't pass preclear, it's not trustworthy.

I do not store that much, but want it to be reliable.  I can find many "new" drives on ebay in the 4tb range.  I tend to buy data center type drives, have always held up well for me in the past.  In this size range, what is the preferred drive?  I currently have a mix of WD gold Re drives and a Hitachi or 2.