I have to change out the hard drives in Raid 1 array. But all the hard drives have the same name in DiskUtility app because they are all the same type of drives from the same manufacturer.

So how can I find out which drive is failing?

I mean, how can I tell which physical drive is referred to by each DiskUtility drive name?

@Allen, thank you for your interest. I have a Mac Pro running Mojave that has 4 drive slots. The first slot holds a 1TB Intel Server SSD with the MacOS installed. There are also three 2TB WD 3.5" SATA Drives that were originally configured in a 6TB Raid 5 array. Disk Util list reveals that the three SATA drives are all the same WD Model number. One of the SATA Drives in the raid array failed and I took it out of the raid array and mirrored the remaining two drives as a raid 1 array. Recently, one of the two mirrored drives also 'failed' from the perspective of the raid array. What I need to do is disconnect both of the 'failed' drives from the raid and copy the data on the remaining SATA drive to an external drive to preserve it and replace the data on a single new SATA Drive, then add two more SATA Drives and re-create a new Raid 5 Array.

So again, my question is: how do I distinguish which physical SATA drive is referred to by the remaining WD drives listed in disk util list is the remaining 'good' drive in the disk util listing that contains my valuable data.

Therefore I believe the question I asked is a proper explanation of the information I am seeking:

how can I tell which physical drive is referred to by each Disk Utility list drive name?

That is, I think the question does not require any information about the drives or their configuration, or their history, or the problems I am having.

Either there is a way for MacOS to tell me which physical drive bay contains which logical drive listed in disk util list, or MacOS has no way of revealing the correspondence between the Logical List of drives in Disk Util and the physical drives attached to the system.

If Mojave cannot tell me which logical drive is which physical drive, then I need to know if there is another utility which will reveal the correspondence.

Does that make sense? Thanks, Kimball

  • How are these drives connected in this array? What is telling you that the array is failing and what RAID level are you using? – Allan Mar 18 '20 at 6:17
  • I need to know how things are connected because if this was hardware RAID, there’s no command within macOS, but since it’s clarified now, I can answer. – Allan Mar 19 '20 at 14:47

You can do this from Terminal with the system_profiler command:

$ system_profiler SPSerialATADataType

It will generate a list of all SATA drives attached to your Mac. You will get an output similar to the following (yours will be longer as you have more drives):

Intel 7 Series Chipset:

  Vendor: Intel
  Product: 7 Series Chipset
  Link Speed: 6 Gigabit
  Negotiated Link Speed: 6 Gigabit
  Physical Interconnect: SATA
  Description: AHCI Version 1.30 Supported


      Capacity: 121.33 GB (121,332,826,112 bytes)
      Model: APPLE SSD SM128E                        
      Revision: CXM09A1Q
      Serial Number: xxxxxxxxxxxxxx      
      Native Command Queuing: Yes
      Queue Depth: 32
      Removable Media: No
      Detachable Drive: No
      BSD Name: disk0
      Medium Type: Solid State
      TRIM Support: Yes
      Partition Map Type: GPT (GUID Partition Table)
      S.M.A.R.T. status: Verified
          Capacity: 209.7 MB (209,715,200 bytes)
          BSD Name: disk0s1
          Content: EFI
          Volume UUID: 0E239BC6-F960-3107-89CF-1C97F78BB46B
          Capacity: 120.99 GB (120,988,852,224 bytes)
          BSD Name: disk0s2
          Content: Apple_CoreStorage
        Boot OS X:
          Capacity: 134.2 MB (134,217,728 bytes)
          BSD Name: disk0s3
          Content: Apple_Boot
          Volume UUID: BFD92A4F-346D-3CCD-911F-48D03D8FD8AE

What you’re going to look for is the disk identifier and the serial number of any drive where the SMART status doesn’t say “Verified”

Once you have the serial number, match it with the label on the drive itself

  • I marked this as the answer because the utility suggested is native to BSD/MacOS. Nice job Allan, Thanks! – Stato Machino Mar 20 '20 at 16:23
  • I much prefer native/built in utilities rather than 3rd party apps. See this answer for another example of system_profiler but about batteries. – Allan Mar 20 '20 at 19:23

The method I use is to grab the serial number from the drive. This information is usually printed by the factory on a label on the physical disk so that it is easy to identify.

Start by ensuring you have HomeBrew installed. Then run the following command to install smartmontools:

brew install smartmontools

Then grab the serial number from the failing drive:

smartctl -a /dev/disk2

This assumes that the failing disk is /dev/disk2 - obviously change that to reflect the disk you have ben reported as failing.

In the output you'll find something like:

Serial Number: C8AF902EAB39

(format varies depending on manufacturer)

You should be able to match that up with the label on the drive.

  • This is a valuable recommendation because it alerts users to the fact that there are utilities that are not included in the BSD/MacOS system that should be researched and evaluated. Thanks for this @jksoegaard! – Stato Machino Mar 20 '20 at 16:25
  • I made my decision about which of these replies was the solution before trying each of them on my system. – Stato Machino Mar 21 '20 at 0:21
  • I made my decision about which of these replies was the solution before trying each of them on my system. What I discovered is that the solution of 'smartmontools' provides a wealth of useful information that is extremely valuable to me in my overall task of correcting the problem with this raid problem. It reminds me to remind others that, just like in the 'wrassles', you have to sell the punch! By informing the requester why your solution is better. @jksoegaard: your solution is superior although the other solution met specific criteria of value (native utility). This is a lesson for all! – Stato Machino Mar 21 '20 at 0:30
  • You can change the accepted answer at any time if you like. In this particular case, I much prefer smartctl over the built-in command. Mainly because you’re dealing with third party hardware - various disks have “oddities” which the Apple util simply doesn’t know about since it’s probably tested mostly with Apple hardware. Smartctl gives more detailed information, but also corrects values that are expressed incorrectly by some specific drive vendors/products. – jksoegaard Mar 21 '20 at 7:46

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