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Fixing an "Unable to write to the last block of the device" Error in OS X®

If an attempt to Erase or Partition an SSD in macOS®  returns the error of "Unable to write to the last block of the device," a few different issues could be causing the error. Try the steps below to fix this error, or to confirm if advanced support is needed. 

1. Change cables and ports

A communication error or some fault in the connection can cause the error. Changing ports and cables addresses this issue. Use an alternate USB port if your SSD is connected externally and change your USB cable or enclosure if applicable. Try the device inside the system if an appropriate internal connection is available. Also, moving the drive to another system entirely, if you have another one available, might help narrow down the problem. 

2. Use Disk Utility in macOS Recovery

If you are receiving the error while you are booted to OS X, using the Erase process in  the Recovery Utilities might help. Boot to macOS Recovery (either by holding Option or Command+R during your system's startup, depending on which your system requires) and attempt the Erase procedure there to rule out other software as a potential source of conflicts.

3. Use alternate software or another operating system

A Disk Utility or OS X variable can be at fault for the error. To determine this, trying different partitioning or formatting software, including, but not limited to Windows® Disk Management, might be a solution. If you format the drive in such an environment and end up using a file system not suited for your needs (such as Windows NTFS when your SSD needs to be macOS Extended Journaled), you can typically move the drive back to your Mac® system and Erase it again, which should now complete after the drive has accepted a format elsewhere. If the troubleshooting above is not effective, please contact us for further support.

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