Home-brew ‘fusion drives’ could be defused into separate SSD and hard disks, then the SSD formatted in APFS, if you wish.Ĭannot currently be converted to APFS.Problems were experienced during beta testing, so do not try. Cannot currently be converted to APFS.Behaviour appears inconsistent, and can also result in errors when formatting or in use.įusion Drives (combined SSD and hard disk, united in CoreStorage): Others can be, at least in Disk Utility, but this must be performed using the Partition tool, not Erase. Disk Utility (High Sierra) either does not offer the option, or returns an error when attempted. Some cannot be converted to, or formatted in, APFS. If you want to convert it to APFS, you must defuse it by uninstalling CoreStorage and turning the SSDs back into separate drives again. CoreStorage – if an SSD is part of a CoreStorage ‘fusion’ drive, even if the other drives are also SSDs, then it will be left in HFS+ and cannot be formatted as APFS.When High Sierra is installed on them from High Sierra, though, it will install onto APFS if so formatted, but does not automatically convert. External – not converted when High Sierra is installed on them from Sierra, no option, and installer will not install from Sierra onto APFS, only HFS+ Journaled.Can be converted from HFS+ Journaled to APFS, and formatted as APFS, using Disk Utility in High Sierra. Left unconverted if High Sierra installed on external drive. Internal – converted to APFS when High Sierra is installed on them, no option.Here’s a brief guide to the different file systems supported by the first release of High Sierra 10.13 on different types of disk.

Install high sierra on external drive