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Best format for external disk?

I have a 2017 MacBook Pro with a 256GB SSD (Apple) installed. Not a lot of space, so I have and external 1TB SSD attached (USB3.1) with many programs and all my data on it. Currently this disk is formatted Guid-HFS+. Is there any advantage to having this SSD formatted as APFS. This disk is NOT bootable and its backup clone is a 1TB partition on a 2TB spinning drive (HFS+). Your thoughts are appreciated.


Also, is it OK for the clone of the boot SSD to be on a spinning APFS drive or is it best on an SSD? I'm guessing SSD. Thanks.


MacBook Pro, OS X 10.11

Posted on Sep 7, 2020 12:20 PM

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7 replies

Sep 7, 2020 12:29 PM in response to Frank Miller2

If the drive is going to be for data only, APFS is better for an SSD and HFS+ is better for a hard drive.


I found out the latter when I bought a new 3 TB external hard drive from OWC. Since every other drive was APFS, I figured it made sense for that one to be the same. But it mounted slowly, and read/write times were much slower than they should have been for a 7200 RPM drive. I called OWC and the tech person there suggested changing it to HFS+. The drive was clearly faster doing everything after changing it.

Sep 7, 2020 10:42 PM in response to Kurt Lang

I guess this applies also to data disks:


"a rotational [APFS] device will never be able to provide acceptable performance as a production macOS startup disk"


https://bombich.com/blog/2019/09/12/analysis-apfs-enumeration-performance-on-rotational-hard-drives


That said, I have an old 2009 2.5" external APFS HDD where I occasionally test Catalina, soon Big Sur (internal SSD is Mojave). Yes, it is slow and takes about 4 minutes to boot.

Sep 8, 2020 6:20 AM in response to Matti Haveri

Yup. I only used the phrase "for data only" because that's what the question was about. Otherwise, it depends on what you're going to do with the drive.


Let's assume you plan on creating two, or a few hard partition breaks on an HDD. If a partition is for data only, then yes, use HFS+. If you're going to install Catalina, then you have no choice but to use APFS for that partition since it's required for Catalina.


But I assume you already know this.

Sep 12, 2020 9:31 AM in response to Kurt Lang

As a follow up to this discussion, I thought that this info might be interesting. When I copied (cloned using SuperDuper) data from an HFS+ formatted SSD to an APFS formatted SSD, I saw copy speeds in the 35-40 MB/s range. I reformatted the HFS+ SSD to APFS and cloned back. The APFS-APFS copy speeds were in the 320 MB/s range. Same computer, same drives, same software - just a changed format on one drive. It appears the HFS+ really doesn't work well on SSD's. These were data-only drives, not bootable.

Sep 12, 2020 9:53 AM in response to Frank Miller2

Good info. One of my external drives is a 1 TB SSD in a USB-C case. That one is broken into four hard partitions and all are APFS. I did try HFS+ for the one that just has backup data on it, but APFS was obviously faster.


Another has a 4TB hard drive, also in a USB-C case. Results were the opposite of an SSD. APFS partitions were always slower than HFS+.

Best format for external disk?

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