Formatting New External Hard drives

Hello all!

This might be a really simple question but I am struggling to find an authoritative answer to it so here I am. I have just bought two new external hard drives for my computer as the time has come to retire their predecessors. I now have a 4TB spinning disk and a 1TB SSD.

I am looking at Disk Utility and am wondering what is the best way to format them. I used to always go Mac OS Extended (Journaled) but would I be better with APFS now? My computer is a 2018 MacBook Pro running Mojave so is already APFS. The two new drives will contain photo and video files. I’ll only be using the drives with this computer.

Thanks.

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Hi @krushe and welcome to the MPU forums!

APFS does not work well with spinning drives, so I would use “Mac OS Extended (Journaled)” for that.

APFS works very well with SSDs, so I would recommend using APFS on an SSD.

The only caveat is that tools like Disk Warrior have not been given enough info on APFS from Apple yet, so they cannot repair APFS drives.

To me that is not a big deal. I think HFS+ was more fragile than APFS and more likely to need a tool like Disk Warrior, but obviously I hope that DW can eventually work on APFS drives too. In the meantime, if you need to repair an APFS drive, your only option (as far as I know) is Disk Utility (which comes with macOS).

Update / Additional Note:

There‘s really no benefit to using an SSD for Time Machine, but if you decided to use an SSD for Time Machine, you would still need to format it as HFS+. I believe that’s the only exception to “Use APFS for SSD” but (again) it‘s not a great use-case for an SSD anyway.

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Thank you @tjluoma. That is very useful information and exactly what I needed. :slight_smile: I’ll take your suggestion and use APFS for the SSD and Mac OS Extended (Journaled) for the spinning drive.

I have a few levels of redundancy built into my backup system so, although I hope to not have to repair/erase a drive in the near future, it wouldn’t mean the loss of any important files.

I’m off to format these drives right now.

Can you expand a bit on why exactly APFS does not work well with regular HDDs?

Thanks a lot

Apple says it’s optimized for SSDs but can be used with HDs.

FYI when you launch Disk Utility it automatically shows the recommended Mac format by default.

I don’t know the why only that I’ve heard it reported by a lot of folks. IIRC Apple didn’t even convert HDDs to APFS when they APFS switchover happened.

HFS+ will keep the drive from fragmenting while APFS will not. Fragmented drives do not hurt performance on an SSD and in fact defragmenting a SSD is a bad idea because of the limited number of write cycles allowed. However fragmented drives can be a big performance hit for HDDs. Apparently there is a task that gets run to defragment HDDs in APFS.

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Mike Bombich of Carbon Copy Cloner did an interesting comparison write-up. He shows how HDs will get some fragmentation and slowdown for the internal drive, but "let’s not throw out the baby with the bath water. APFS has loads of really nice features, like snapshots and volume space sharing. Managing volumes within an APFS container is a dream compared to the older method of preallocating space to specific partitions. It’s important to understand why we might expect to see performance differences between the two filesystems and when that might impact your use of the filesystem, but this one performance aspect on its own isn’t enough reason to avoid it."

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

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Thank you! That makes sense :ok_hand:

On the Bombich Software (publisher of Carbon Copy Cloner) website there are easy-to-follow instructions for preparing (formatting) external drives to be used for backups. The link below contains instructions for different versions of macOS - Catalina, Mojave, High Sierra, Sierra and El Capitan. Included are instructions for APFS and macOS Extended Journaled.

https://bombich.com/kb/ccc5/preparing-your-backup-disk-backup-os-x#high_sierra

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My personal experience of putting APFS on a spinning drive was an eye opener. I decided it would be a good idea to move my photo collection (not Apple Photos) onto an APFS external hard drive.

The issue you run into quickly is that it becomes REALLY SLOW to open directories in Finder. The reason for this is that directories are stored sort of like files — when you create a new one it grabs some free space to store it. This means your directories are all over the disk and take time to seek to. This compares to HFS+ where all of the directory structures are in one place and therefore quickly accessed as you traverse your directory tree.

As you can imagine, on an SSD there is no significant penalty to whizzing all over the disk to get directory structures.

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