splitting a partition

[zoran]

I cant splitt a partition i have created in an ext hdd. I have split the main drive into 3 partitions (A,B,C) and now i cannot split partition B to two partitions B1 and B2. Should that be possible or not using DiskUtility or any other app?

 

[Fishrrman]

I wouldn't split a drive into TOO MANY partitions.
3 or 4 is "enough".

I would suggest an app named "iPartition".

There used to be two very useful utility apps for OS X:
- iDefrag
- iPartition

Both were published by a company called Coriolis Systems that has now discontinued them, because changes in the Mac OS and the move from platter-based drives to SSDs has diminished the need for the above apps.

However, some folks may still have a need for them.
Coriolis has graciously made available all previous versions of their software.

You can freely download them from here:

Coriolis Systems

 

[zoran]

Thanks but i dont see iPartition for ElCap. I downloaded an older version 3.6.0 and its not allowing me to place it in Applications.

 

[DeltaMac]

If the external drive has APFS containers, you can easily add a volume to any container, rather than adding another partition.

And, there can be reasons where more partitions/containers are quite nice. I have a 1TB drive which has 24 partitions, including bootable installers for all Mac systems from 10.4 Tiger, to 11 Big Sur. Also have some of those systems installed, mostly for testing on older Macs, for multiple versions of older OS X (and macOS) fully installed systems, with, of course, the basic Apple software, and a few utilities that I use for a variety of purposes. And, a partition dedicated to keeping copies of the original OS X installer apps that I have downloaded through the years, plus other major apps that I might have a need to install quickly, such as MS Office 2004, etc.

The only reason that I might limit the number of partitions/containers is that the desktop gets a bit messy with a dozen or more drives popping up!

@zoran - when I go to that old Coriolis page that Fishrrman posted, there are 4 different versions of iPartition. One is version 3.5.1, for 10.10 and 10.11. That's the one you want for your ElCap system. If you donwloaded the version 3.6.2, then, yes, it's for 10.12 and 10.13 - won't work on ElCap. (I don't see ANY version 3.6.0 on that page)

 

[zoran]

#DeltaMac the Partition of the ext hdd drive, i wish to split into two partitions is not an APFS, its MacExt.

 

[DeltaMac]

Yeah, Apple's Disk Utility/Partition tab is a bit stubborn sometimes.
In Disk Utility, you want to make sure you have the device selected, then the partition tab.
That will show the partitions, as you have them set up. Click on the one you want to split.
Then, click the (+) under the partition layout.
That should show in the graphics that the partition split. Click on the "B2" partition, and change the name to something else (just to modify more than just the partition configuration).
You can ALSO change the size of the split partition, if you have a need to make the split something different than just one half of the original. Just change the size box to whatever you might need. I use that function to make bootable installer partitions, typically 8GB in size. (Or just leave the size as is, all depends on your needs.) But, just reminding you that you don't have to leave the size as the split makes it.
And, when you are ready, click the Apply button.
The re-partition process can actually take a bit of time to complete, sometimes several minutes. I have been fighting with a PCIe SSD M.2 card, usually extremely quick, that a simple split like you want takes nearly 10 minutes to complete. (I have decided that m.2 card is recyclable 🙂

If that doesn't work, where in that process do "things" stop?

 

[Quackers]

Wouldn't you need to click on the B partition and shrink it to an appropriate size then create a new partition in the space that has left?

 

[DeltaMac]

Wouldn't you need to click on the B partition and shrink it to an appropriate size then create a new partition in the space that has left?

Yes, but I think you could only do that on the last partition, not an internal partition like the OPs B out of A, B, C partition setup.

 

[Quackers]

Yes, but I think you could only do that on the last partition, not an internal partition like the OPs B out of A, B, C partition setup.

I've definitely done that but I couldn't say for sure it wasn't on the last partition.
It's been a while 🙂
Unfortunately I don't currently have a partition that I would want to mess about with at the moment in order to confirm.

 

[zoran]

Then, click the (+) under the partition layout.

Oh cool 🙂

 

[DeltaMac]

I have around 20 external drives here. Looked at a sample of my drives with multiple partitions. Some allow modifying/adding partitions, and some drives do not allow that.
I don't know what the difference is. Some drives are nothing but OS X extended, others are a mix of macos and APFS volumes. Doesn't seem to matter, some can modify partitions, some drives cannot. There's nothing that I see that changes that, other than a reformat of the complete drive. I should point out that I keep track of the service life of these drives. All operate normally, and pass testing.
There are no significant differences between the drives, but some show the partitions are editable, some do not.

And, I don't think that indicates that something is "wrong", only that there's something different, and it's not something that I can detect.
One drive is my primary Mac system installer, with custom partition sizes for each of 15 partitions, and I rebuilt that drive less than 6 months ago, including a full erase, and now can't modify any partition size, nor add a new partition.
It's an external SSD, not a spinning hard drive. I have another external SSD with a very similar, multi-partition setup, and that one is fully editable.
(?) It's a mystery. I'll solve it. I'll erase that SSD again, and rebuild it from nothing. Because I can, and I have everything available to rebuild the drive completely. There's nothing on the drive at the moment that I don't have on at least 3 other drives.
Unfortunately, that isn't a great help for you, as I just don't know what happened.

 

[zoran]

No worries, i did your steps and all is solved ;-)