MacOS – Unmounted hard drive times out ejecting or mounting

disk-utilityexternal-diskhard drivemacosmount

I have a Drobo connected via Firewire to my MBP which is causing me some issues. Here is the diskutil info:

Device Identifier:        disk2s2
   Device Node:              /dev/disk2s2
   Whole:                    No
   Part of Whole:            disk2
   Device / Media Name:      MacDrobo

   Volume Name:              Mac Drobo

   Mounted:                  No

   File System Personality:  HFS+
   Type (Bundle):            hfs
   Name (User Visible):      Mac OS Extended
   Journal:                  Unknown (not mounted)
   Owners:                   Disabled

   Partition Type:           Apple_HFS
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 FireWire
   SMART Status:             Not Supported
   Volume UUID:              A97C9EAF-E18F-3BE3-80CD-8A8C6FB6E8E7
   Disk / Partition UUID:    3776B4B3-8530-495E-A413-AFB0A221281B

   Total Size:               2.2 TB (2200000000000 Bytes) (exactly 4296875000 512-Byte-Units)
   Volume Free Space:        0 B (0 Bytes) (exactly 0 512-Byte-Units)
   Device Block Size:        512 Bytes

   Read-Only Media:          No
   Read-Only Volume:         Not applicable (not mounted)

   Device Location:          External
   Removable Media:          No

It is not mounted but it is still very active in reading and writing…I can hear it thrashing about. When I try to eject or mount I get time out errors, when I try to run verifyVolume, I get a bit more of a complex error.

MacTravis:~ travis$ Sudo diskutil eject disk2
  Volume timed out while waiting to eject

MacTravis:~ travis$ Sudo diskutil mount ReadOnly disk2
  Volume on disk2 timed out waiting to mount

MacTravis:~ travis$ Sudo diskutil verifyVolume disk2s2
  Started file system verification on disk2s2 Mac Drobo
  Verifying file system
  File system check exit code is 8
  Error: -69845: File system verify or repair failed
  Underlying error: 8: POSIX reports: Exec format error

I assume my computer is doing something in the background as when I unplug the drive it stops being active, and becomes active again when I plug it back in. I have tried using Disk Utility to see what is up but if the drive is plugged in then DU never loads completely, if its open then I plug in the drive nothing shows up. Is there any way to see what is going on with the drive, if OS X is fixing it in the background, or what is going on?

Best Answer

Looking at the total size of the disk I suppose you are hit by the 2.2 TB limit of MBR partition tables.

Since block addresses and sizes are stored in the partition table of an MBR using 32 bits, the maximum size as well as the highest start address of a partition using drives that have 512-byte sectors (actual or emulated) cannot exceed 2 TiB−512 bytes (2,199,023,255,040 bytes or 4,294,967,295 (2^32−1) sectors × 512 (2^9) bytes per sector). Alleviating this capacity limitation was one of the prime motivations for the development of the GPT.

So repartition the disk with a GPT partition table.

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