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Create a macOS High Sierra Bootable USB Drive. A clean install wouldn’t be possible without creating a macOS High Sierra Bootable USB drive. So let’s go ahead and create one! Find an 8 GB USB stick and make sure it is formatted as GUID Partition Map and Mac OS Extended (Journaled). To check if it is, launch the Disk Utility application. Select Disk Utility in the window. In the next window, select the drive where you want to install High Sierra. In most cases the name should be “Macintosh HD.” 6. In the Erase Tab, click Erase with Mac OS X Extended (Journaled) type. When it is done, you get a clean drive. Quit Disk Utility, Access to Install MacOS item.
![Sierra Sierra](/uploads/1/2/5/6/125637752/816832520.png)
Speculation initially pointed to a reliability issue with converting existing Fusion drives to the APFS format. But the real issue may be a performance hit taken by the hard drive component of the Fusion pair.
![Utility Utility](/uploads/1/2/5/6/125637752/631058758.jpg)
One of the features of APFS is a new technique to ensure data protection called Copy-on-Write. Copy-on-Write keeps data loss to a minimum by creating a new copy of any file segment that is being modified (write).
It then updates the file pointers to the new copies after the write is successfully completed. While this ensures data is protected during the write process, it can also lead to a great deal of file segmentation, scatter parts of a file around a disk. On a solid-state drive, this is not much of a concern, on a hard drive, it can lead to.