In my pool I had a 4TB drive that Scanner said has 2MB of damage, so I told DrivePool to remove the drive from the pool, but there was probably a hundred or so GB of files I was unable to read to get off the drive, so I told DrivePool to forcibly remove the drive from the pool, since those files could be recovered in other ways (with some effort). About six months later I discovered that drive had a bad SATA cable, and I quickly moved the remaining files off the drive (manually), so I didn't lose anything whatsoever, except the 2MB of damaged files, which were duplicated, so it wasn't an issue there either. Since I figured the SATA cable was probably the only problem all along, I removed all partitions from the drive and created a new partition with a full (not "quick") format, to ensure everything was good -- then I ran Burst Test for nearly a day, which it passed -- the the drive seemed good to go for being re-added to the pool.
That's where things are confusing me. I added the drive to the pool, and I see there's a red arrow for "New un-duplicated file placement limit", which is zero, and I can't quite figure out why. Scanner still complains that the drive is damaged, so I disabled the option to remove files from damaged drives... but the red arrow is still at zero. I am wondering if DrivePool could be confused, since I had told it to remove the drive from the pool six months ago, but that was before I repartitioned, reformatted, and readded it to the pool.