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Help! Please! My Mac Pro 5,1 SSD/HDD does not mount at all

I have a Mac Pro 5,1 (2012 mid) and I installed a new 2.5” 1TB HDD (with adapter) into the Mac (Bay 2). But My Mac does not even recognize the drive. I took out the drive, and moved the OS HDD to the same slot and it booted just fine. So I know the port is fine. I then took the HDD out of the adapter, put the computer on its side, and manually placed the new drive into the tray port. I made sure it was secure/supported to avoid any damage to the port but still have no luck. I then went and grabbed a SATA to USB adapter and plugged it into the External USB on the case. The Mac instantly noticed the drive, mounted it, and even let me install the OS to the drive. I can even boot from the USB mounted drive. Any suggestion?

Best Answered by

iBoysoft author Jenny Zeng

Jenny Zeng

Answered on Wednesday, November 22, 2023

The new drive won't work internally until it's properly partitioned and formatted for use on Mac.

Does the new drive show up in Disk Utility when connected internally? 

If it does, is it grayed out? If the new drive appears in Disk Utility but appears to be unmounted, you can select it and click the Mount button to manually mount it. Besides, check its partition map. If it's formatted with Master Boot Record, reformat it with GUID Partition Map.

Follow the steps below to format the drive for Mac:

  1. Open Disk Utility from the Applications > Utilities folder.
  2. Select this drive from the left sidebar and click "Erase."
  3. Set the Scheme to GUID Partition Map. (Very important !!)
  4. Choose a proper file system. Select APFS if it's going to be used on macOS 10.13 or later. Otherwise, select Mac OS Extended (Journaled).
  5. Give the drive a name like Macintosh HD.
  6. Click Erase again.

If your drive doesn't show up in Disk Utility, it's recommended to reformat it after placing it in the USB enclosure and connect it to your Mac externally. Use the same steps mentioned above. Once the new drive is successfully formatted, you can reattach it to your Mac internally and check if it works now.

If that doesn't help, grab another 2.5-inch and 3.5-inch drive and check if your Mac recognizes them when connected internally. 

If your Mac recognizes the 3.5-inch but not the 2.5-inch, the problem likely lies on your 2.5 to 3.5" adapter. In this case, change to a different adapter.

If your Mac doesn't recognize both of the drives or both drives, you need to replace the SATA hard drive cable.

Read more:

[Solved] How to fix SSD not mounting on Mac?

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