Formatting and partioning an external HD with APFS and GUID

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Formatting and partioning an external HD with APFS and GUID

I have recently purchased a 4TB external HD. I want to use it to back up my 1TB MacBook, both with Time Machine and Shirt Pocket Super Duper. I also want to have partitions to back up my photos and videos, so four equal partitions. If I understand correctly, the GUID partition is flexible, so rather than having 4 rigid divisions of 1TB each, the 'walls' move to accommodate the various needs of the partitions.

Up until now, I've only been using Super Duper as my backup but, with a luxury of storage capacity now, I thought it wise to also have a Time Machine backup. I've never used Time Machine before, but I understand that it keeps creating new copies until the disc is full, whereupon it starts overwriting the oldest. My fear is that, with flexible divisions, Time Machine could take over the whole of the free space on the 4TB disc, creating problems for the other partitions (Super Duper, Lightroom photos, and Video files). Have I understood correctly ? If so, is there a way of giving a maximum to a GUID partition, so that Time Machine is limited to a 1TB share of the pie ?

I look forward to your advice, thanks, Stuart

MacBook Pro 14″, macOS 12.1

Posted on Jan 4, 2022 2:55 AM

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Answer 1

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Jack-19

Level 8

45,700 points

Jan 4, 2022 3:08 AM in response to I never quite fully understand

Hi, Stuart, and welcome to the Apple Support Communities.

For what you want to accomplish, you really should have three external drives. One drive should always be dedicated just for Time Machine and another just for a clone. They should not be shared. Then, for storing general external data, that needs another drive.

Not only can using a drive for multiple purposes cause issues, but it is a big risk for loosing data. If you store certain files on this external drive not backed up elsewhere while the drive is serving as multiple backups, if that one drive fails, there goes everything. Both backups, data that wasn't stored elsewhere, etc.

Assuming you have a newer USB-C/Thunderbolt MacBook Pro, here are some excellent external drives that Apple sells:

You should then store data on one external drive, and that backups to your separate Time Machine drive that also backups your MacBook. You can then have a separate bootable clone (which should be an SSD for good performance, should you ever need to use it and boot from it: G-Technology G-DRIVE mobile SSD R-Series Storage - Apple).

I hope this makes sense.

Jack

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Answer 2

Jan 4, 2022 3:47 AM in response to Jack-19

Hello Jack,

Thanks for your prompt and clearly explained reply. My new 4TB disc will free up some other 1TB external HDs that I have, so I'l simply reconfigure how I'm going to use them. I'll keep separate 1TB drives for Time Machine and Super Duper, then store all my data backup (Video, photos and other stuff) on the partitioned 4TB drive. It's a backup, so if it fails, I still have the original, while I rush out and buy a replacement. It makes sense to have my MacBook backed up on two separate discs, kept in separate locations.

As per my question about the GUID partitions I will set up on AFPS on the 4TB drive (now just for data) did I understand correctly that the 'walls' move in relation to the storage needs, or are they fixed according to how I set them up ?

Thanks again,

Stuart

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Answer 3

Jack-19

Level 8

45,700 points

Jan 4, 2022 3:52 AM in response to I never quite fully understand

Per File system formats available in Disk Utility on Mac - Apple Support,

Apple File System (APFS), the default file system for Mac computers using macOS 10.13 or later, features strong encryption, space sharing, snapshots, fast directory sizing, and improved file system fundamentals. While APFS is optimized for the Flash/SSD storage used in recent Mac computers, it can also be used with older systems with traditional hard disk drives (HDD) and external, direct-attached storage. macOS 10.13 or later supports APFS for both bootable and data volumes.

APFS allocates disk space within a container (partition) on demand. When a single APFS container has multiple volumes, the container’s free space is shared and is automatically allocated to any of the individual volumes as needed. If desired, you can specify reserve and quota sizes for each volume. Each volume uses only part of the overall container, so the available space is the total size of the container, minus the size of all the volumes in the container.

So, yes, all volumes on an AFPS drive share space within a "Container", and as the needs of volumes within the Container change, it adjusts as needed.

Jack

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Formatting and partioning an external HD with APFS and GUID

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