Samsung T3 cannot be unmounted or converted to APFS

Change your View (View drop down on the toolbar) to Show All Devices then you will see your device name with your volumes indented underneath. Select the device name instead of a volume; then click Erase and you should see the Partition Scheme selection for GUID.

I think I solved this... (after an hour of trying different things).

From what I can see High Sierra Disk Utility no longer gives the options of choosing a scheme (GUID vs MBR) when formatting a drive. (I've submitted a request to Apple for them to put it back in). APFS needs a GUID partition.

(See below, it used to look like this before High Sierra, but now the third option is gone)

Screen+Shot+2017-10-09+at+9.18.42+PM.png

I ended up taking my external HDD and plugging it into a Windows 10 computer, using Disk Management to convert to GUID and then tried to convert the drive to APFS. (Note APFS isn't even an option when erasing a disk in MBR format, but when erasing the drive after converting to GUID it gave me the option).

However, I ended up having issues because I couldn't convert the drive to APFS or even to Mac OS Journaled after it was converted to GUID. It gave me errors stating that there is not sufficient free space on the drive. (Even though I had just wiped it clean): "Mediakit reports not enough space to complete operation"

I figured out how to fix the "Mediakit reports not enough space to complete operation"... Follow the instructions from this Youtube video: https://www.youtube.com/watch?v=Rqico9ENA-4

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Now, this is very embarrassing for Apple, but after some hard work, and a Windows 10 computer I was able to solve the error: com.apple.StorageKit error 118

You could try uncoupling the Photos Library from Photos and see if that works.

AFPS is only supported on SSD. T3 is a SSD, but Mac OS doesn`t recognize it as one. You can see this if you open the disk utility and select the T3. Then Press CMD+I to show the details. In there you will see it is not recognized as SSD.

If this is a driver issue or a HighSierra thing, no idea.

But as long as it doesn't show up as SSD, AFPS will not work.

If the T3 is seen as a "rotational" drive rather than an SSD, it won't be converted because the drive's firmware isn't reporting it as an SSD.

There are some OWC SSD drives that suffer from the same issue; I don't believe there's a fix as of yet for either.

OK, having GUID works... all fine now

SnakeDog wrote:

...

From what I can see High Sierra Disk Utility no longer gives the options of choosing a scheme (GUID vs MBR) when formatting a drive. (I've submitted a request to Apple for them to put it back in). .....

I see all these options for an external drive with Disk Utility:

GUID - APFS, HFS+, FAT, exFAT

Encrypted and case sensitive for HFS+ and APFS

MBR & Apple Partition Map - HFS+, FAT, exFAT

Case sensitive but no encryption for Mac format

William is right that if the drive displays as an HDD it won't automatically convert. However, I've converted multiple external HDDs to APFS with no issues. (They run much faster and have more free space now). Note, I would be very careful manually converting a boot drive. I've only converted my externals which if they corrupt isn't the end of the world as I have it all backed up.

Mr. Luigi, you indicated that if you go to 'info' it is identified as an HDD. That's why the assumption is that the firmware is not reporting itself properly to your computer.

Thanks William,

Do you have any backup for this? From what I'm seeing from Apple's documents APFS should work on anything, except they turned off the auto upgrade for boot drives that are HDD and Fusion.

I've converted two external drives to APFS (HDD) without issue, they run great. But the third drive (WD Essentials 1TB) is giving me the same "com.apple.StorageKit error 118".

Sorry @Korinna, but you are mistaken AFPS works on HDDs just like it does on an SSD:

From Apple's documentation:

https://developer.apple.com/library/content/documentation/FileManagement/Concept ual/APFS_Guide/FAQ/FAQ.html#//apple_ref/…

Can I use Apple File System with my existing hard disk drive?

Yes. Apple File System is optimized for Flash/SSD storage, but can also be used with traditional hard disk drives (HDD) and external, direct-attached storage.

I've also tested it and upgraded several HDDs to APFS now. It works just fine and does make things run faster, even on a Hard disk.

What you are thinking about is that in the final release of High Sierra Apple didn't turn on APFS as an automatic upgrade for HDDs. They never said why, but it seems like perhaps there were some upgrade concerns, or perhaps concerns about running APFS on a boot drive. But I haven't found any documentation on this. Several users have installed APFS on their boot HDD and it seems to work fine with some minor tweaks. It seems to me that it's likely that APFS caused some issues during the automatic upgrade. (The posts I've read are mostly total wipes on HDDs, not upgrades with the data saved for boot drives.)

But like I said, external drives HDDs can be upgraded to APFS no problem, without loosing any data. I've done it several times, so have others.

If I am inadvertently hijacking this thread, I apologize. Let me know and I'll remove this.

I also have a Samsung T3 SSD installed on my 2012 Mac Mini. But, it is my BOOT Drive. I have designated the original internal HDD as my backup drive using Carbon Copy Cloner. I just updated to High Sierra and have observed the same things others have mentioned. The T3 was not converted to APFS. In "info," the T3 is not identified as a SSD. Also, when I go to disk utility, select the T3, and click on "Edit" the option to "Convert to APFS..." is greyed out. So, I can't manually force the T3 to convert to APFS. Should I just let sleeping dogs lie and keep the T3 as a HFS+ drive, or is there some safe procedure I can implement to get the T3 to accept APFS? The Mini "screams" using the T3 as the boot drive. So fast. But, if I don't run any risks, I'd love to have it "scream" even louder. :-)

Feed me speed.

Thanks, William. I am just going to be happy with my current set-up and hope that Apple addresses this.

Maybe Tim Cook should spend less of his time and resources courting pop music stars and provide more support and resources for his software development teams.

Well...that wasn't very kind on my part. It just slipped out. 😉

Neither Apple nor Mr. Cook can correct errors from devices misreporting what type of drive they are.

If a drive reports it is not an SSD, macOS won't try to convert it to APFS - operating exactly as it should.

Hi Snake Dog, Thanks for your continued participation in this discussion! Two things:

1. I totally agree with your caution about "forcing" a conversion of my T3 boot drive to APFS. I have decided to wait until Apple issues a formal update that allows my T3 Boot Drive to update to APFS. Of course, this assumes Apple will issue an update! Fact is, the performance of my 2012 Mac Mini is SOOOOOOOO much better using the T3 as a Boot Drive using the old file system I have no reason to complain.

2. I did say my T3 was not reporting itself as a SSD in info. But, I don't think it was reporting itself as a HDD either. I think that section was simply blank. Someone is not talking. Or, someone is not listening. OR BOTH!