Arghhh

If you're using the 2.2.0.651 or more recent beta, there was a change that is likely causing this.
 
You can manually disable this, if you want:
http://wiki.covecube.com/StableBit_DrivePool_2.x_Advanced_Settings
Set "BitLocker_PoolPartUnlockDetect" to "False", and reboot the system.
 
 
 
And yes, the StableBit DrivePool Service is absolutely critical. It performs the balancing and "after the fact" duplication passes. it's also what powers the UI and remote control functionality. 

I use two of the Seagate 8TB archive drives for an unduplicated backup pool from my media server.  99% of the data is write once and I will saturate my network link.  I have my pool set up to keep free space the same on both drives so usually it will alternate writes between the two drives giving them more opportunity to do their background processing and rewrite shingles if needed.  I didn't do a full disk check or write and read zeros to the drives before I put them in use.  I heard this may make the drives consider any future write as a rewrite and make the speeds slower.  For media or backup they work perfect.
 
I run a robocopy mirror script from the network shares to the pool nightly and so far it's the easiest backup solution I have found.