If a disk goes missing while the computer is running, Drivepool handles this as expected. It pops up a notification and e-mails me, and I can take action. However, I've noticed its handling of a disk that's missing upon bootup is less than optimal. When the UI is started, it simply says that the service is not started, though the service is actually running. What's on the disks still available also seems to be readable. And, of course, no notification of any sort, which is a problem on a headless server.
I am running v2.2.0.651 BETA. Hopefully this will be fixed in a future version.
I'd also like to make a request for both Drivepool and Scanner. I'd like an option for a when a notification of a drive problem or missing disk appears, a sound can be made through the motherboard speaker. This could be helpful for headless installations where someone other than me may be using it or I may not have my phone by me.