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

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If an attempt to Erase or Partition an SSD in Apple OS X return the error of "Unable to write to the last block of the device," a few different issues may be at fault. Try these steps to easily fix this error or confirm if more advanced support is needed.


1. Change cables and ports


A communication error or some fault in the connection can cause this error. Changing ports and cables addresses this. 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 internal SATA connection is available. Also, moving the drive to another system entirely if you have another one available may help.


2. Use Disk Utility via macOS Recovery


If you are attempting this within OS X, the same process with minimal interference from other applications running within the operating system may help this error. 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 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. If so, moving to alternate partition management or formatting software, including but not limited to Windows Disk Management, may 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 Mac OS Extended Journaled), you can typically move the drive back to its intended environment and Erase it again, now successfully after the drive has accepted a format operation elsewhere.


If the methods above are not effective, please contact us for further support.