Am 07.02.20 um 16:49 schrieb o1bigtenor:

Running a Raid-10 array made up of 4 - 1 TB drives on a debian testing
(11) system.
mdadm - v4.1 - 2018-10-01 is the version being used.

Some weirdness is happening - - - vis a vis - - - I have one directory
(not small) that has disappeared. I last accessed said directory
(still have the pdf open which is how I could get this information)
'Last accessed 2020-01-19 6:32 A.M.'  as indicated in the 'Properties'
section of the file in question.

Has been suggested to me that I make the array read only until this is resolved.
I have space on the the array on a different system to recover this array.
Suggestions on how to do both of the above would be aprreciated

directories on a filesystem on top of a RAID don't disappear silently -
my bet is a simple drag&drop move or deletion aka PEBCAK