MediaKit reports partition (map) too small" in Disk Utility

I recently upgraded my 1 TB external hard drive to a 2 TB hard drive. Using Disk Utility, I erased the new hard drive, formatting it for Mac OS Extended (Journaled) and all is well until I decided to partition it into 2-1 TB partitions. I got a message stating "MediaKit reports partition (map) too small. If you recently grew your whole-disk, you should run whole-disk repair. : (-5341)". What is the problem, or what is whole-disk repair? I've erased the disk again, I've run disk repair on the disk, but nothing works.

Mac Studio M2 Max

Taho 26.1

Mac Studio, macOS 26.1

Posted on Nov 17, 2025 7:24 AM

Top-ranking reply

neuroanatomist

Level 9

55,875 points

Posted on Nov 18, 2025 11:37 AM

Ok, thanks for trying. You are not paying close enough attention to HWTech's post.

Notice how in your screenshot there is no Scheme option at all. That means you have not selected the top level of the drive. You only think you have, but you've selected the volume not the drive. You probably see something like this:

Go to the View menu and select Show All Devices:

After that change, you will see the actual drives. Note below they are "Apple SSD..." and "Samsung PSSD T7...," names of manufacturers and products, not OS-/user-applied volume names like 'Macintosh HD' or 'Backup'.

Now, you can see and select the actual top level of the drive and with that selected, when you click Erase you should see the option to select the partition scheme. That's what is currently set to Apple Partition Map and what you need to set to GUID.

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19 replies

Revelstokian Author

Level 1

8 points

Nov 18, 2025 9:57 AM in response to neuroanatomist

I have used Macs since 1992. I teach people to use a Mac. I've formatted many hard drives before. This time, I've had a problem and posted it here. What I'm trying to point out is that, I'm not receiving the normal formatting options, as I showed in my screenshot. I've done everything that's been suggested, but nothing's changed...I only get the two formatting options and even though DU shows that the drive is 2 TB, when I erase the drive (I remind you that it's a new empty hard drive) I only receive the two options. I assume (maybe incorrectly) that it's something to do with the firmware on the enclosure and due to the age of the enclosure, I can't find any update. I guess I'll just have to use the drive with no partition, that's all.

Revelstokian Author

Level 1

8 points

Nov 17, 2025 12:07 PM in response to neuroanatomist

It's odd, I don't get those selections...as you can see.

Nov 17, 2025 12:31 PM in response to Revelstokian

Shouldn't matter. What matters is that you're using a partition scheme that is for Macs from >20 years ago.

Nov 17, 2025 9:51 AM in response to Revelstokian

What partition map are you using? Should be GUID. I suspect you selected Apple Partition Map, that's an old format (about which Apple states, "Choose this option for compatibility with old PowerPC-based Mac computers."), because with that option you will only see MacOS Extended and FAT options.

APFS can certainly be used with HDDs (the reason I mentioned MacOS Extended makes sense for spinning disks is that APFS is a bit hard on them since it intentionally fragments files for storage efficiency). When I connect an HDD and click Erase in DU, I see APFS options as long as I am using the GUID map that's appropriate for modern Macs (modern being relative, since it includes Intel Macs in this case).

Assuming my suspicion is correct and you are using Apple Partition Map, switch to GUID (it's the 'Scheme' setting) and try again. One big difference is that partitions on an APM map cannot be resized, but they can on a GUID map. You can still use MacOS Extended Journaled as the format for your HDD (unless your intent is to use Time Machine with the drive or a partition on it, then it must be formatted with APFS or TM won't use it).

MediaKit reports partition (map) too small" in Disk Utility