I just purchased the Western Digital My Passport Ultra 3TB disk (old model WDBBKD0030BBK-NESN) for use on my MacBook Pro 15 inch mid-2015 running OS X El Capitan 10.11.6. I plan to use the drive as a backup for a backup. The original backup has 3 partitions of 1 TB each partition. While trying to figure out if Carbon Copy Cloner would automatically create partitions on the destination drive (i.e. the WD My Passport Ultra), I stumbled upon this info on CCC's website: "Some versions of OS X have difficulty recognizing USB devices that have been encrypted with FileVault. The Western Digital My Passport Ultra 3TB disk, for example, works fine as a bootable device when not encrypted. In our tests, however, this device was no longer recognizable when FileVault encryption was enabled. This problem appears to be limited to OS X 10.11 El Capitan. The same volume was accessible using older and newer OSes, and also functioned fine as an encrypted startup device using older and newer OSes." Searching online, I found an instance of one person experiencing this, but haven't seen any others. Has anyone experienced their WD My Passport Ultra or other USB drive becoming unrecognizable upon encrypting with FileVault? I haven't opened my drive yet and would rather just return it if is incompatible with OS X 10.11 and FileVault.