Apple - 3rd party SSD with High Sierra
If I install High Sierra on a 3rd party SSD, will it be APFS?
An SSD is a drive regardless of who makes it and will be compatible APFS.
In this article, about SSD support for OWC (3rd party) SSDs, there are two main take aways:
OWC shows up as both a rotational drive, which won't convert upon setup and as a RAID 0 array which won't convert at all.
A user in the forum confirms that the Crucial M4 in a 2012 MBP works without issue.
So, the issue is (IMO) not a High Sierra one, but one of the manufacturers in how they implement their SSD and present it to the OS.
It's not clear from your question whether you want it to be APFS or not, but not all 3rd party SSDs have been compatible with macOS High Sierra's installer. Apple is aware of this and is working to address this in future updates, but it's unclear at this stage which SSDs will be supported or not.
However, if you're hoping that your SSD will work with APFS then your best bet is to just try installing macOS High Sierra. If the installer detects a problem with the APFS conversion it will cancel the install.
Finally, if you want to install macOS High Sierra and the installer doesn't allow this, then many users have found they can still install macOS High Sierra through a rather long-winded process.
NOTE: I strongly recommend you have a reliable backup of your data before commencing the following process!
- Clone your current SSD to an external hard drive
- Boot your MBP from the external hard drive
- Now install macOS High Sierra to the external drive you've just booted from
- Reboot your MBP again from the external drive (so that you've now booted up in macOS High Sierra)
- Reformat your SSD as APFS
- Now clone your external drive to your SSD
Once you've finished you can reboot into macOS High Sierra from your SSD.