Just wanted to post this to the internet since there are literally no other posts about this exact scenario, which I could see others running into. Short story - I lost 2 drives in a 4-drive parity array.
I had a shotty storage spaces array in my home desktop comprising of 2x2TB WD Green drives, 1x2.5TB Seagate Green, and a 2TB WD Red in a Storage Spaces array. A small mirror volume spreading all 4 drives was created first, which would host my critical files (this array never failed, by design), and a parity array that filled the remaining capacity, which also spread across 4 drives. I ran in this configuration for over a year before experiencing hardware failures.
First off - Never run green drives. I don't care your reasons for wanting to buy them or receive them for free (sell them if you do), but I've lost several dozen green drives over the last few years. They will fail! They're bottom bin drives that didn't make the cut.
I upgraded my computer case (Cooler Master's HAF XB Evo Lan Box is incredible and worth every penny), and while doing so, accidentally dropped two powered-off green drives about 3" onto a soft surface. I can only deduce that this is what caused the drives that worked pre-case-upgrade to fail. Upon booting the system back up, Storage Spaces started throwing notification errors at me that 1 drives was missing. So I hopped into powershell and ran get-physicaldisk, and one of the drives wasn't showing up in the list. After some quick troubleshooting, I determined the drive was not spinning up after receiving power, and had experienced a major hardware failure. No ability to raw copy any data off the disk, even with external hdd docks. 100% dead. Cool. But with 4 drives in a parity array, I should have been able to see all of the virtual disks and volumes in a reduced resiliency state. When attempting to bring the storage pool online, it would fail and I'd get a notification that there were issues.
So over to event viewer, I found "The device, \Device\Harddisk1\DR1, has a bad block." A quick note - as far as I'm aware - you cannot run chkdsk or other similar utilities on a physical disk that is part of a array. So how to fix bad sectors? I spent some time trying to figure out which device DR1 was, but ended up just running Western Digital's LifeGuard's Diagnostic tool, extended test, on the three remaining physical disks since it can scan drives for bad sectors without depending on an in-tact file system. Two of scans completed fine without issue, but one of them failed the test due to too many bad blocks that it couldn't repair. So how to remove the bad blocks? Fortunately for me, this HDD with bad blocks still spun and raw data could be read, so I placed the bad-blocked drive in a USB dock and ran HDD Raw Copy to a good working drive (3TB instead of 2, but the system didn't care too much). After placing the good drive with the cloned data, I booted up and... the array came online! Storage Spaces was smart enough to not look at UUIDs, models, sn, friendly names, etc, and knew that the totally different drive had the data on it that it needed to complete the array. 95% of my data is perfectly intact. A large video file didn't copy over, but everything else was good to go.
So for other users who experience bad blocks in their storage space array, know that HDD cloning might save you assuming the data on the drive is intact enough.