How can I disable Write Caching for an external drive using my MacBook Pro on Sonoma?

SalvatoreCo wrote:

Thank you Barney, mount worked but when I type the command: amount/dev/disk1s1 the terminal says: no such file or directory. which command to disable write caching for my new adata external drive usb4.

The command you’re using is trying to mount the 1 partition (after the ”s”) on the 1 disk, though the command you’ve shown does need a space between the mount and the device. That command is also “mount”, not “amount”, and the device name will vary by devices present and partitioning used or used.

Since you’ll undoubtedly want to learn more about this directly (and will not leave the default caching enabled), the command is:

mount /dev/devicename

With the option I suspect you’re headed for:

mount -o noasync /dev/devicename    # syntax in general
mount -o noasync /dev/disk1s1       # for disk 1 partition 1

To get the names of the devices and partitions configured:

diskutil list

To get more details about a particular device (and this’ll be the base device name, and not the “s” partition name):

diskutil info /dev/devicename

As for shell command syntax, both spaces and the lack of spaces is significant. Spaces are how the shell finds “hunks” of the command, which means including or excluding spaces as necessary.

I’d suggest leaving caching enabled. Caching usually gets I/O out to the device more efficiently. And with whatever caching scheme is used, macOS does want to get the I/O out to the storage as faster as it can manage. Yanking out a device at any moment still runs the risk of a partially completed I/O operation even with caching disabled, as active apps will routinely write various sectors in various places as part of some particular I/O operation.

This write-up indicates the opposite:

https://aphnetworks.com/reviews/adata-se920-1tb/4

”If you go into the [Windows] Device Manager, you can enable write caching. However, this means you will need to safely remove the hardware to disconnect the SE920 1TB properly. In Mac OS, write caching is enabled by default. In response, all of the tests have been conducted over three interfaces: USB4 via Thunderbolt 4, USB4 via Thunderbolt 4 with write cache enabled, and USB 3.2 Gen 2x2. We will see how this affects the results on the next pages.”

“Particularly in the write test, you can see the effect of enabling write caching, as disabling it turned the SE920 1TB into the slowest drive with a peak write of 249.15MB/s.’

Personally, I’d plug it in and try it, and see if write caching is even an issue. I’d be more concerned about TRIM support, generally. This as SSDs can have poor erasure performance.

I’d suggest discussing this with ADATA product support however, as they know their hardware best.

SalvatoreCo wrote:

because Im planning to buy an ADATA SE920 USB4 40Gbps Type-C External SSD which on the review shows that the writing speed on Macs slow down too much when the write caching is enabled.

I couldn't find that device for sale on Newegg. I'm kinda skeptical about a solid state device that has been un-solid-stated. It has moveable parts and apparently needs a fan. That's a red flag. And apparently people are saying that it isn't Mac compatible without low-level hacks. That's two red flags.

What are you planning on using this drive for anyway?

SalvatoreCo wrote:

which command to disable write caching for my new adata external drive usb4.

Why do you want to do this?

does is disable it permanently or when the laptop reboot the caching is enabled again? if is permanent how to enable the caching again?

have great week end Barney :)

No idea. I just know how to read the syntax for the commands.

SalvatoreCo wrote:

I couldn't find any low level hack for Mac on web, did you? with MAC we cannot even update the firmware. I will use it for video editing raw files.

I only looked for the drive itself being sold on Newegg. That's a good place for reviews. If Newegg doesn't have 500 5 star reviews, why would you buy it? I'm not saying those reviews are accurate, but that ADATA device isn't even sold on Newegg. I see it on Amazon, but there are no reviews at all on Amazon. My Samsung T7 Shield with the flaky USB port has 863 reviews on Amazon with 85% being 5 star. I wouldn't recommend it at all.

My recommendation would be to let a few other people try out that device first.

run isn't a command.

mount should work.