Chosen Solution

I am trying to install Windows on Mac Pro 5.1 using boot Camp Assistant, but she won’t play nice and displays the following pop up The startup disk cannot be partitioned or restored to a single partition. The startup disk must be formatted as a single Mac OS Extended (Journaled) volume or already partitioned by Boot Camp Assistant for installing Windows. Disk Utility shows a single partition 4tb drive. ‘diskutil list’ reports the following, dev/disk0 (internal, physical):    #:                       TYPE NAME                    SIZE       IDENTIFIER    0:      GUID_partition_scheme                        *4.0 TB     disk0    1:                        EFI EFI                     209.7 MB   disk0s1    2:                  Apple_HFS Macintosh HD            4.0 TB     disk0s2    3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

/dev/disk1 (external, physical):    #:                       TYPE NAME                    SIZE       IDENTIFIER    0:      GUID_partition_scheme                        *1.0 TB     disk1    1:                        EFI EFI                     209.7 MB   disk1s1    2:                  Apple_HFS Install macOS High S… 90.9 GB    disk1s2    3:                  Apple_HFS bup macpro              364.0 GB   disk1s3    4:                  Apple_HFS Untitled                544.7 GB   disk1s4

disk0 is the boot drive where I am trying to install Windows. Disk1 is WD external drive used for TM backup etc. I am planning on installing a 500GB SSD as the boot disk (cloned from disk0) when the partition impasse is resolved. Are all these partitions in disk0 essential? I can’t remove the partitions in Disk Utility as they don’t appear. Can I safely merge/delete the partitions in Terminal? Am I missing another solution? Many thanks

Lets backup here you don’t want to clone! Cloning software will mess you up! What you do want to do is do a full proper OS install to your new drive, then use Migration Assistant to move your user accounts, apps & data over. As you have a larger boot drive installed now than what you are planning on using you will likely need to trim down what you install with Migration Assistant. I would strongly recommend you don’t move your data files over as you do want to leave enough free space for the OS to leverage for caching and paging. As a rule of thumb I leave 1/3 on 250 - 512 GB drives and for larger 1 TB and larger 1/4 free on all boot SSD’s. As for the partitions you need them all on disk0 0 - Is nothing more than the boot record and the drives full size GUID_partition_scheme1 - Is the EFI firmware image EFI EFI2 - Is your true data volume Apple_HFS Macintosh HD3 - Is the hidden recovery partition Apple_Boot Recovery HD As to why BootCamp won’t install its likely due to the size of your drive! 4 TB is likely confusing the tool. Once you get your SSD installed and setup you should be fine.