Might be, but then only sda would spin up.
You say that all services are stopped, but your Running Processes log shows that the user "olivier" is logged in and using the sftp server, so olivier home folder is being accessed (on md1, RAID1, both disks) and that might wake up the disks.
It might also be a swap issue, you have swap setup from RAID1 (inherited from D-Link setup), have you touched the "swapiness" value?