After updating to Mavericks, none of my external drives will sleep. I have tried waiting while the system is live and putting the system to sleep - neither option spins them down. This wasn't a problem on 10.8... just wondering if anyone else has had this problem and if they have a fix. I am running Mavericks on a Late 2009 iMac. I have 2 WD My Book Studio IIs connected and daisy chained via Firewire 800. "Put hard disks to sleep when possible" is checked in Energy Saver.