CentOS - Dec 2020 - Software raid Oddity

I have a CentOS 7.9 system with a software raid 6 root partition. Today 
something very strange occurred. At 6:45AM the system crashed. I 
rebooted and when the system came up I had multiple emails indicating 
that 3 out of 6 drives had failed on the root partition. Strangely I was 
able to boot into the system and everything was working correctly despite

 > cat /proc/mdstat

also indicating 3 out of 6 drives had failed. Since the system was up 
and running despite the fact more than 2 drives had failed in the root 
raid array I decided to reboot the system. Actually I shut it down, 
waited for the drives to spin down and then restarted. This time when it 
came back the 3 missing drives were back in the array and a cat 
/proc/mdstat indicated all 6 drives were again in the raid 6 array. So a 
few questions:

1.) If 3 our of 6 drives of a raid 6 array supposedly fail, how does the 
array still function?
2.) Why would a shutdown/restart sequence supposedly fix the array?
3.) My gut suggests that the raid array was never degraded and that my 
system (i.e. cat /proc/mdstat) was lying to me. Any Opinions?

Has anybody else ever seen such strange behavior?
-- 
Paul (ganci at nurdog.com)
Cell: (303)257-5208

On Wed, 16 Dec 2020 13:57:13 -0700
Paul R. Ganci via CentOS wrote:
> My gut suggests that the raid array was never degraded and that my 
> system (i.e. cat /proc/mdstat) was lying to me. Any Opinions?
I wonder if it's a ram failure in either the main computer or the drive
controller.  An intermittent ram failure (or cold solder joint or something
equally hard to track down) could cause all manner of un-repeatable weirdness.

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