How to identify problems with Linux Raid?

Question

linux

There is a home server with soft raid 6 configured using mdadm.
The problem is that sometimes on it some files become zero length, and sometimes some files disappear. But, the fact is that I don't know this for sure, I have never been able to catch a raid on the fact that the file was and then disappeared, or that it originally had a size and then disappeared. Perhaps the file was originally with zero length, or was missing.
How can I check the integrity of the raid, identify problems, recover lost files, recover damaged files?

uname-a

Linux home-server 4.4.0-103-generic #126-Ubuntu SMP Mon Dec 4 16:23:28 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

cat /proc/mdstat

Personalities : [raid1] [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid10]
md0 : active raid6 sdf1[7] sde1[8] sdd1[5] sdc[9] sdb1[1]
5860145664 blocks super 1.2 level 6, 512k chunk, algorithm 2 [5/5] [UUUUU]

file -s /dev/md0

/dev/md0: Linux rev 1.0 ext3 filesystem data, UUID=88178a98-6333-4e75-bf03-7ee7f0b67e88 (needs journal recovery) (large files)

Answer 1

if everything is fine in /proc/mdstat (judging by the output, everything is OK), then all the questions are about the file system, what fs do you have?

Answer 2

Lost/corrupted files, this is not to the raid layer, which works with blocks and knows nothing about your files, but to the file system layer that is on it.
So look towards fsck and similar tools.