On 2014-12-17 9:36 PM, NeilBrown wrote:

Curious.

What does "mdadm --examine" report for each device immediately after boot,
before you try assembling anything?

Maybe also get the output just before you shut down to compare.

NeilBrown

Sadly, I had to disassemble this array and get something workable that 
didn't become unassembled on every restart. I did try sticking all 
drives on the same AHCI controller, which caused the array to be 
resynced on every restart instead of disassembled.

I suspect this issue is caused by bcache (I'm using the md as a backing 
device for bcache.) The bcache maintainer states "get the md people or 
someone to explain _what_ they want whatever has their device open to do 
on reboot."

I'm going to setup a test environment and see if I can reproduce it again.

-Peter