Storage Space with warning: "Reduced Resiliency"

B R, sorry but have never used storage spaces so no experience in this area.  Can only suggest that checking each drive individually with the tools provided by the drive maker is the way to identify which particular drive is the source of the errors you are seeing.

The only other thought would be to look at the Windows event logs to see if they contain anything that would lead to a unique identifier for a single drive from the storage space?

Thanks for the suggestions Steve.

Had a look in Event Manager but cant find anything relevant so far.

Looking for a disk health checker from the drive maker is a good idea. WD in this case.

I just checked when I first set up these WD 4TB Red Label drives as a mirrored storage pool and they've been happily running for 6 years without a squeak. So that aint bad at all.

6 years for the drives sounds very good as 4TB drives must have been fairly new at that time!  I have seen much younger drives die without ever getting beyond 1 or 2 years!

Cannot add anything to what Steve has said. A remote possibility is that there is a loose connection or that the SATA cable or power cable to the HDD is failing. I have seen the former from time to time, the latter very rarely.

Life span is good. I have a WD AV drive which has spent most of the last 9 years in a video recorder and it is still going strong … no indications of possible errors. I have WD Red 4TB drives in my NAS purchased on 4 February 2015 which are still going strong. Also have 2 WD VelociRaptor 600gig purchased in May 2012 still going storng (the third one failed a few years back).

Ian