I've noticed that inactive disks in my system are no longer entering standby (spinning down) despite being issued "atactl <device> setstandby <timer>". These are backup drives, regular SATA drivers attached to the internal SATA bus on the mainboard, and they see no activity whatsoever outside of an isolated nightly 15 minute period. After messing around with it a little bit I noticed that they actually do spin down immediately after I throw "setstandby/sleep" at them, but something wakes them up again after less than 60 seconds, despite that the file systems and the devices remain completely untouched and unreferenced.
I found that if I unmount the file systems everything about the standby/sleep behavior works like it always used to in the past. Somehow, by just being mounted, something in OpenBSD is now periodically nudging the disks and waking them up from standby. For now I've had to resort to a very klutzy workaround by keeping the disks unmounted outside the backup window to preve - that is, mounting them before backup session and then unmounting and putting them to sleep again afterwards. I can't say exactly when this started happening, the system sits in a corner in my home so I don't have "ears on it" regularly.
