Is My Disk Speed too Slow?

[Mimiron]

Hey, I'm on an 27-inch iMac 2017 looking for advice regarding disk speed. It has a Fusion Drive and I'm externally booting from an NVME M2 drive with an enclosure that's supposed to handle 10 GBPs. However, the disk speeds I'm getting are pretty ridiculous. It's 921 MB/s write and 936 MB/s read. Is that normal?

https://imgur.com/YpaC2Hx

On my 2018 Macbook Pro, I'm getting 1830 MB write and 2582 MB/s read. Would it maybe help to put the M2 ssd directly into the iMac instead of booting externally?

My CPU Intel Core i5-7500

Thanks for any advice.

 

[BrianBaughn]

What model NVME M2 drive, what model enclosure and via what port is it connected?

 

[Fishrrman]

"I'm externally booting from an NVME M2 drive with an enclosure that's supposed to handle 10 GBPs. However, the disk speeds I'm getting are pretty ridiculous. It's 921 MB/s write and 936 MB/s read. Is that normal?"

Those speeds are "better than normal" for a USB3.1 gen2 enclosure.
They're very good.

1000MBps would be the "theoretical top speed".
But one never gets that -- it's theoretical, not "real world".
936MBps reads are about "as good as you're going to get".

Stop worrying about it and be happy...

(by comparison, what speeds do you get from the fusion drive?)

 

[Mimiron]

"I'm externally booting from an NVME M2 drive with an enclosure that's supposed to handle 10 GBPs. However, the disk speeds I'm getting are pretty ridiculous. It's 921 MB/s write and 936 MB/s read. Is that normal?"

Those speeds are "better than normal" for a USB3.1 gen2 enclosure.
They're very good.

1000MBps would be the "theoretical top speed".
But one never gets that -- it's theoretical, not "real world".
936MBps reads are about "as good as you're going to get".

Stop worrying about it and be happy...

(by comparison, what speeds do you get from the fusion drive?)

Unfortunately, I couldn't download BlackMagic or any other tool that measures disk speed while booting from Fusion Drive because I couldn't log in with my Apple ID and my account got locked for some reason even though I've put in correct login credentials. Thanks for confirming the speeds are better than normal.

 

[gilby101]

It has a Fusion Drive and I'm externally booting from an NVME M2 drive with an enclosure that's supposed to handle 10 GBPs. However, the disk speeds I'm getting are pretty ridiculous. It's 921 MB/s write and 936 MB/s read. Is that normal?

Yes, that is pretty good.

I suspect you may be confusing bytes and bits. The 10 GBPs you are quoting for the USB connection, the B is bits and should be written with a small b, as in 10 Gb/s. Since there are 8 bits in a byte and there is some overhead, a figure around 1 GB/s (that is B for bytes) is best expected.

And yes it is confusing. But it is standard for interconnects (USB, wifi, Ethernet, etc.) to be measured in bits/s which is abbreviated with a small b, whilst disk throughput is in bytes/s which is abbreviated with a big B..

 

[Nguyen Duc Hieu]

Hey, I'm on an 27-inch iMac 2017 looking for advice regarding disk speed. It has a Fusion Drive and I'm externally booting from an NVME M2 drive with an enclosure that's supposed to handle 10 GBPs. However, the disk speeds I'm getting are pretty ridiculous. It's 921 MB/s write and 936 MB/s read. Is that normal?
On my 2018 Macbook Pro, I'm getting 1830 MB write and 2582 MB/s read. Would it maybe help to put the M2 ssd directly into the iMac instead of booting externally?

My CPU Intel Core i5-7500

Thanks for any advice.

Test the enclosure on your MacBook Pro.
It might get better, but not double or something.
I guess you have got the best speed of that enclosure with your iMac.
Maximum theory speed for your USB enclosure is about 1200MBps.
(1200MBps is equivalent to 1200 x 8 Mbps, B = byte = 8 bits = 8b)
Maximum theory speed for nVME (gen 4) now is 7000MBps read and 6000MBps write.
No Mac can achieve that speed at the right moment, only Windows PC can.