Bitlocker encrypted system drive causes hourly spin-up of all other HDDs

Question

Cleanly installed Window 10 Pro v1511 with 3 internal SATA disks, old BIOS w/o TPM.

Once the system drive is encrypted with password protected Bitlocker, my other two drives spin-up from standby on every full hour of uptime, like clockwork.

When this happens Task Scheduler history shows no tasks ran at the time, Resource Monitor and ProcMon show no file activity on both of the drives, no corresponding Windows event log entries.

The only clue I got is DiskMon reporting exactly one read for each of the sleeping disks: sector 2048 with length 16. Unfortunately it doesn't show what process is doing this, but looking at ProcExp would suggest PID 4 System is the only thing hitting the disks at the time.

My search-fu is failing me, I can't even find anyone else describing the issue. Obviously, I don't want my disks to wake up every bloody hour of the day for no reason whatsoever and I'd rather not go back to VeraCrypt or leave the drive unencrypted.

Is there some tweak/workaround for Bitlocker to prevent this? Any ideas why this would happen in the first place?

Answer 1

So, at last I found two more posts by people affected by the issue over on the Microsoft forums, unsurprisingly no solution by the clueless and less than helpful support drones.
The first poster mentions two possible workarounds though:

• turning off Bitlocker Drive Enryption Service
• taking drives offline in Disk Management

Haven't tried the latter but disabling the service worked for me and contrary to its description, my drives still auto-unlock and I haven't noticed any downsides.
I'd ask wtf it does then and if turning it off is a stupid idea somehow, but at this point I doubt anyone at MS even knows.
So thanks, banantaffer! Maybe it helps anybody else running into this.