APFS Encrypted: slow write speed on magnetic disks

You are far out of date with your Sonoma installation. The current version is v14.7.1. I recommend that you apply that update. Your Software Update panel will likely show Sequoia v15.1 and if you scroll downward, you will see a link named something like an additional update is available. If you click on that you will see Sonoma v14.7.1 and probably Safari 18.1 available for installation. When selected these, and not Sequoia will be updated.

The operating system and APFS are intended for solid-state drives that have orders of magnitude performance gains over rotational drives. Encryption/decryption will take a toll on performance. Especially on rotational drives.

You should check if your QNAP RAID has any outstanding firmware updates available for it and apply those. Is that USB 3.1 cable rated for Gen 2 (10 Mbps) performance or is it a Gen 1 cable (5 Mbps)?

Your Sonoma v14.1.1 is far too early for Apple to have applied any performance updates to it so v14.7.1 may make a difference despite your drives in use.

Even if you chose the 16 GB RAM option for your M1 mini, it may not be sufficient for your applications that are running and the QNAP overhead.

You should have a look at this technical article:

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

It is 5 years old but I believe it is still valid.

"After the very first simulation, APFS starts at a deficit — APFS takes three times as long to enumerate a million files on a rotational disk compared to HFS+ enumerating the exact same collection of files on the exact same hardware. This result on its own is staggering. As you add and remove files from the volume, however, the performance continues to decline. After just 20 cycles, APFS enumeration performance is 15-20 times worse than HFS+ performance."

I use a number of external mechanical drives as Time Machine and SuperDuper target backup drives, none (except one, see below) are set up as RAID. All of mine are APFS. I have never seen write speeds as low as 30 MB/s; when I have checked the speeds were always 80 MB/s to 100 MB/s. I also use some external SSDs for Time Machine and SuperDuper clones, and those achieve 500 MB/s to 1000 MB/s. The computer I measured these on is a 2019 MacBook Pro. I "measure" write speed simply by noting that, say, a 400 GB initial clone or initial Time Machine backup took about an hour from start to finish on a mechanical drive and about 10 minutes on the SSD. That said, these differences are not really noticed doing incremental backup updates because those are so quick, maybe less than a minute, or sometimes a few minutes.

But it sounds like you are doing serious production work not just incremental backups. Based on the article referenced above, you will see very significant slowdowns with APFS on mechanical drives for production work, and it will get worse over time.

I am wondering if you would be much better off using HFS+ for the mechanical drives in the manner you are using them.

I do have one RAID 0, an older Seagate drive that has been in use for more than 10 years. That is a pair of mechanical drives, HFS+, and it achieves 200-300 MB/s, much faster than what I have seen with individual mechanical drives on HFS+ or APFS.

I think the combination of APFS on mechanical drives plus the overhead of RAID and of encryption are combining to degrade your throughput.

I'd like to add my own observations, as I ran into exactly the same issue with the same enclosure (QNAP TR-004) but with 4 x 20TB Toshiba HDDs, configured as 60TB RAID5 volume, connected to macOS 14.7.1 Sonoma computers.

• Not encrypted APFS performance is OK - about 220-250 MB/s write speed for video files.
• Encrypted APFS is a disaster. The write speed drops to 15-20 MB/s. 10 times!
• I see no difference between Intel (Mac Pro) or Apple Silicon (M1 Mac Mini).
• I used bundled USB 3.0 cable, changing it makes no difference, the link speed is as it should be.
• Under macOS Sequoia 15.1 the transfers were even a bit worse.
• Reconfiguring the enclosure as non-RAID / individual drives and writing to one of 20 TB HDDs gives proper speed (150 MB/s, no matter APFS is encrypted or not).

Unfortunately encrypted HFS is no longer an option, and we need the data to be secure, the enclosure is stored in public office spaces.

I completely don't understand what is going on. Our company opened a support ticket in Apple, because right now I even don't how to avoid such hardware purchases in the future. They are currently investigating.

Does the QNAP support the UASP protocol for USB3.x? If so, is UASP shown in the System Profiler for that connection?

In order to utilize UASP, every device in the direct chain from drive to computer must also support UASP.

cazoirarc264 wrote:

I don't see anything about UASP in the documentation of the QNAP (other models do include it), and I don't see any mention of that for any of my drives in System Information. But other people report reliable 200 MB/s transfers with the QNAP, and my HFS+ disks that also don't mention UASP can write at 160 MB/s.

The individual single drives within the enclosure have nothing to do with UASP. UASP is about USB transfer protocols.

If your QNAP is connected to the system with USB3.x and it does not support UASP, then that is a huge hindrance due to how the older USB transfers worked. UASP is even more important if you have any non-UASP devices sharing the same USB bus with the QNAP since any non-UASP USB devices will interfere with the USB3 transfers. I personally will only use USB3.x devices that support UASP since their USB controllers are usually a bit higher end.

Good quality USB3 cables are also needed...if you are using an adapter, then that is another point to cause problems. Make sure to disconnect all other external devices from the computer so that they are not in the equation. Also, the longer the USB cable the more likely for performance issues.

Can you test the transfer rates of the RAID from the OS of the QNAP device to make sure the issue is with the external transfers? I've never used a QNAP so I'm not sure what is possible here.

Have you looked at System Information to make sure the drive is connected to a high-speed bus?

Perhaps it is connecting at USB2 speeds for some reason.