#Os x completely reformat usb drive install#

One of the 2TB drives was my timeMachine backup, so all backups in that timeMachine are now lost. I am losing MASSIVE amounts of data when this problem occurs (fortunately most data is backed up elsewhere though). Even after all of this maintenance, I've still experienced this same drive re-formatting on insertion of external drives. I've zapped my PRAM, I've run FSCK, I've updated permissions, run all cron tasks, run 'Clean My Mac', flushed all caches, etc.

These utilities simply see the re-formatted drive and declare that the drives have no errors or issues found.

I've tried running apple disk utility on the erased drives. Sometimes when I insert the drives listed above they mount as normal and display the HFS file structure and all file contents, on other occasions there is a short delay (approx 40 seconds) after inserting a drive, after which the drive is mounted as though it is brand new, straight out of the box the 'hidden' EFI drive mounts on the desktop, along with a now blank and reformatted HFS drive partition. The problem is affecting WD MyBook 2TB external drives (x2), WD MyBook Duo 12TB NAS, and also SD & CF memory cards from my digital DSLR via a Lexar Card Reader.

#Os x completely reformat usb drive install#

Since recent install of OS X 10.11.6, my MacBook Pro now completely reformats my external USB drives upon insertion (approx 20% of the time).