I am running OS X 10.10 on a Mac Pro and I am connecting a 2TB My Book VelociRaptor Duo to it via Thunderbolt. If I leave the drive formatted in RAID everything works just fine. I need it formatted in JBOD, but whenever I do so, the drive mounts for about 3 seconds and automatically ejects itself. After it ejects I can see it in Disk Utility, where I can right click and mount it again, but it still only stays mounted for about 3 seconds. Can anyone help? I can't even use this drive because of this.

  • How is the formatted in RAID? one drive on its own is not RAID
    – mmmmmm
    Aug 21, 2015 at 17:50
  • That's besides the point - it works just fine when formatted in RAID. I need it in JBOD and when I format it like that it automatically unmounts within three seconds. I need the drives to stay mounted.
    – mturch
    Aug 22, 2015 at 19:27
  • When formatting the drives, are you using the software provided by Western Digital (WHD Drive Utilities), or Apple's Disk Utility app?
    – IconDaemon
    Aug 22, 2015 at 22:31
  • Can you capture the system logs when this happens? Can you reproduce it on a clean OS or new user account?
    – bmike
    Aug 29, 2015 at 2:36
  • I actually just formatted it using Apple's disk utility instead of WD's software and have not had a problem since.
    – mturch
    Nov 19, 2016 at 5:06

2 Answers 2


I have the exact same problem with a WD My Passport Pro 4 TB.

When formatted in Raid 0, it mounts as a 4 TB disk and stays mounted as expected.

When JBOD'd as two 2 TB disks, they mount, and then unmount 3 seconds later, remount and re-unmount until they stop mounting. Disk Utility sees both disks and will remount them, but won't mount them durably.

Interesting remark : this happens in Yosemite 10.10.5. In Mavericks 10.9 AND, astonishingly, in El Capitan 10.11 beta 7, my My Passport Pro JBOD'd twin disks mount and work absolutely as one would normally expect !

  • Found the problem !!!
    – Yves M
    Aug 30, 2015 at 11:18
  • Found the problem !!! Easy fix : Users and Groups / Opening tab (for helper apps to open at Startup), and suppress WDDriveUtilityHelper, which is installed there when the WD Drive Utilities is opened for the first time. Now, both JBOD disks mount an stay mounted, together with all the custom partitions I've made.
    – Yves M
    Aug 30, 2015 at 11:26
  • That didn't help me - all i did was format it into JBOD using WD Drive utility, then repaired each disk in mac disk utility and it started working fine.
    – mturch
    Sep 22, 2015 at 19:54

Oh! It's same things happen to me. I could use it by JBOD format after few weeks. But recently It suddenly start 'UN-mount' behavior. I use iMac5k 2014 with OS X 10.10.5 (14F27) I tried another TB cable, but fail.

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    – n1000
    Aug 26, 2015 at 14:46
  • All i did was format it into JBOD using WD Drive utility, then repaired each disk in mac disk utility and it started working fine.
    – mturch
    Sep 22, 2015 at 19:57

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