Resolved Cannot partition external drive using ExFAT file system

[rhimbo]

iMac Late 2015, macOS 10.15.4...

I'm trying to partition and format my Western Digital 3TB external drive. I erased the entire disk. There are two partitions,
2 TB - ExFAT
1 TB - MacOS Extended (Journaled) - Time Machine back up partition

I just now reformatted the 2 TB partition to ExFAT. It was MacOS Extended.
I'd like to split the 2 TB partition into 2, 1 TB partitions. But the "+" and "-" signs are grayed out.
However, when I select the 1 TB partition (MacOS Extended), I can select the "+" and "-" buttons.

It appears that macOS does not support partitioning (splitting) a partition formatted as ExFAT. Is this true? Is there a way I can do this?
Would it work instead to reformat the entire drive as MacOS Extended, then split it into 3, 1 TB partitions and then reformat each partition to ExFAT?

I've attached screen grabs.

I'm actually interested in learning the "why" not just the "how to just get this task done." Please feel free to explain or point me to some documentation. I tried doing some internet searches but couldn't find anything that explains how it works and why. I'm not sure if it's related to the EFI.

Thanks....

 

[Taz Mangus]

Would it work instead to reformat the entire drive as MacOS Extended, then split it into 3, 1 TB partitions and then reformat each partition to ExFAT?

That sounds like the best way to accomplish it.

 

[ApfelKuchen]

You can't partition a partition. You'd have to create a third partition.

You're right, this has nothing to do with EFI.

 

[rhimbo]

Perhaps I did not articulate clearly. I know that I cannot "partition a partition." But you can add a partition to a disk. Using Disk Utility, the only way to do this that I know is to select the partition you want to split and then click "+" to "add" a partition.... You're not really adding a partition to the selected partition; you're adding a partition to the disk, but doing so by "splitting" an existing partition -- resizing the selected partition to make unused disk space from which you create the new partition.

After reformatting both the 1 and 2 TB partitions to have type MacOS Extended, I was able to successfully "split" the 2 TB partition into two 1 TB partitions. Now I have 3, 1 TB partitions, all of type MacOS Extended.

However, notice that Disk Utility overrode the partition names to "WD Passport" for all 3 partitions. I could not rename the partitions as I specified, "WD Passport disk2s1", "WD Passport disk2s2", etc.

So it appears that one has to first ensure all partitions have a native macOS file system type. And, for non-macOS file systems, apparently one cannot edit the partition name.

Hmm, I wonder how this is going to work when I'm looking at my mounted file systems....

New screen grab attached. I'm going to try to copy files to this now. If this doesn't work -- if Apple really does not support ExFAT, then I guess it's remote rsync to backup my files to a Linux system....

 

[joevt]

Partition name and volume name are two different things. Edit the volume name in the Finder. The gpt command can be used to rename a partition. Or use one of the commands from gpt fdisk. Or try iPartition (it's not supported anymore, doesn't support APFS partitions, but it shouldn't break them either while you deal with the non APFS partitions).

Apple supports ExFAT partitions but maybe it doesn't support resizing them? I'm not sure if iPartition supports resizing ExFAT.

 

[Taz Mangus]

It looks like the reason that the names all turned out to be WD Passport is because it seems the name length for ExFAT is restricted to 11 characters. I just tried creating a ExFAT partition and was restricted to 11 characters. You can still rename the partitions in Finder though.

 

[rhimbo]

Ah...! Thank you...! Yes, that worked. I renamed the partitions to "WD disk2s1", "WD disk2s2" and "WDdisk2s3".

I had to quit Finder and open new windows after un-mounting and remounting.
I'll try to rsync to it and see if that's successful.
Then I'll ensure I can read the file systems from Windows 7 and Linux.

That was the original point of this effort. Platform-independent back up and "business continuity".

[automerge]1590967334[/automerge]

Partition name and volume name are two different things. Edit the volume name in the Finder. The gpt command can be used to rename a partition. Or use one of the commands from gpt fdisk. Or try iPartition (it's not supported anymore, doesn't support APFS partitions, but it shouldn't break them either while you deal with the non APFS partitions).

Apple supports ExFAT partitions but maybe it doesn't support resizing them? I'm not sure if iPartition supports resizing ExFAT.

Volumes logical file systems sitting on the virtual "disk" associated with a partition? Correct?

I imagine that there must be a 1-1 correspondence between volumes and partitions. Is that correct?
It seems that you can mount only one volume on a partition at any given time?

I think Apple's "container" is a logical structure that can cantain more than one volume. Is that correct? I seem to have read that recently. Is the volume a similarly logical (virtual) file system.

 

[joevt]

Volumes logical file systems sitting on the virtual "disk" associated with a partition? Correct?

Close enough. On a GPT formatted disk, each GPT partition can have a partition name.

Compare the following:
gpt -r show -l /dev/disk2
diskutil list /dev/disk2
gpt shows the partition name.
diskutil will show the volume name when possible (if the partition is not a container or whatever)

It should be noted that your disk2 might not always be number 2. It will have a different number if you boot from a different disk or have different disks connected to different ports.

I imagine that there must be a 1-1 correspondence between volumes and partitions. Is that correct?

It seems that you can mount only one volume on a partition at any given time?

Not always. An APFS partition is a container with multiple volumes. A partition that is part of a RAID set is only part of a container that contains a partition.

I think Apple's "container" is a logical structure that can cantain more than one volume. Is that correct? I seem to have read that recently. Is the volume a similarly logical (virtual) file system.

APFS file system or raid or fusion disk or whatever. It's hard to keep track of all the different options.

You can check diskutil list to see all partitions, containers, synthesized disks which are formed from one or more partitions.

diskutil info -all will give more info on everything.

 

[rhimbo]

I think I get it. I'm not going to get into the precise details, but I think I understand what you're saying.

Forgetting containers for a moment, in the Apple world, a volume can represent an abstraction of a file system. It can be a virtual file system. Under the covers it can actually manage multiple mount points that, say, comprise a RAID volume? It could also define a logical file system that maps it's real data onto the physical file system on the physical disk partition. Something like that?

And containers can contain multiple volumes. I'm sure some of this might be wrong, but, conceptually I get it.

Thanks.

 

[joevt]

I think I get it. I'm not going to get into the precise details, but I think I understand what you're saying.

Forgetting containers for a moment, in the Apple world, a volume can represent an abstraction of a file system. It can be a virtual file system. Under the covers it can actually manage multiple mount points that, say, comprise a RAID volume? It could also define a logical file system that maps it's real data onto the physical file system on the physical disk partition. Something like that?

And containers can contain multiple volumes. I'm sure some of this might be wrong, but, conceptually I get it.

A file system is like HFS+ or NTFS or APFS or FAT. Some type of media contains a file system - usually this is a partition or set of partitions (for RAID, etc.) or it could be a file (a disk image) or RAM I guess (I haven't dealt with a RAM disk in forever). A disk image could contain partitions or a single file system. A file system usually has a volume name. APFS is kind of special - it contains multiple volumes that share the same media.

There is the root directory. This usually points to the startup volume. In unix, it has a path of "/"
Other volumes are mounted and have a path that points to them. The path points to a folder that represents the volume. in macOS, these mount points are located at "/Volumes/" but could be anywhere. Use mount to get a list of mount points.

 

[chabig]

I'm actually interested in learning the "why"...

I don't know but I suspect that Disk Utility can't resize ExFAT partitions. They are resizable on PCs, but Disk Utility is a macOS tool primarily for Macs, so it doesn't make sense for Apple to put in the work required to support every feature of non-native filesystems.

 

[rhimbo]

@chabig, I think resizing of ExFAT does not work very well at all. I tried it this morning and it kept failing, even though my disk is empty. And no information other than "failed." Yesterday I successfully created 3 ExFAT partitions with names less than the 11 character limit. Can't imagine why it doesn't work. Everything looks fine from df, diskutil, etc.

I don't like anything Microsoft, so, on one hand I can understand why Apple would not put a lot of effort in this. And I would have to lean towards APFS being a better file system than ExFAT or NTFS. Nevertheless, there is something to say for interoperability. I don't see a good argument for Apple not supporting EXT4 or even other common industry file systems such as Solaris VFS.

Well, if it works that's good enough for now. Today I'll use rsync to back up my hard drive. Then I'll test to make sure I can actually read it from Windows 7 and Linux.

 

[rhimbo]

I forgot to update this thread... The solution was to format the drive with all ExFAT partitions. Apparently you cannot mix and match macOS file systems with non-Apple file system types.

 

[joevt]

I forgot to update this thread... The solution was to format the drive with all ExFAT partitions. Apparently you cannot mix and match macOS file systems with non-Apple file system types.

Not true. Bypass Disk Utility.app and use the command line or iPartition.app