Slow External SSD Read Speed on Catalina.

[runebinder]

Hi,

I just got an Asus ROG Strix Arion NVMe SSD enclosure (USB 3.2 Gen 2), and a Sabrent Rocket Q 2TB to go with it. I've got a small 80GB Bootcamp partition and Paragon NTFS so decided to have two partitions; a 1.5TB NTFS partition and a 500GB Mac OS Extended (Journaled) partition.

Ran a Blackmagic Disk Speed Test on the drive and the write speed is fine, weirdly the read speed is hovering around 170-180Mbps on most tests. Rebooted the Mac into Win 10 Bootcamp and downloaded and ran CrystalMark. Same port & cable but now seeing around 1,050Mbps for the read as expected.

I did also try it on my desktop PC with the supplied USB C to A cable. The port is 3.2 Gen 1 and getting around 450Mbps on CrystalMark, which makes sense with the slower speed.

So it has to be something on the macOS side, any ideas of what it might be?

 

[Fishrrman]

Could be the SSD.
Could be the enclosure.
Could be the cable.
Could be your partitioning arrangement.

Or a combination of factors.

I sense that it has something to do with the fact that you have the drive partitioned in a way that may be difficult for the Mac to "digest". Could be a driver/interface issue. Could be something else. Hard to say.

I'll make a suggestion, realizing that it might be unacceptable to you:
ERASE the drive on the Mac to Mac OS extended, journaling enabled, GUID partition format. Then run BlackMagic on it again (as an "empty" drive).
Does that change anything?

 

[runebinder]

Could be the SSD.
Could be the enclosure.
Could be the cable.
Could be your partitioning arrangement.

Or a combination of factors.

I sense that it has something to do with the fact that you have the drive partitioned in a way that may be difficult for the Mac to "digest". Could be a driver/interface issue. Could be something else. Hard to say.

I'll make a suggestion, realizing that it might be unacceptable to you:
ERASE the drive on the Mac to Mac OS extended, journaling enabled, GUID partition format. Then run BlackMagic on it again (as an "empty" drive).
Does that change anything?

It can't be the SSD, enclosure or cable otherwise the same issue would happen in Windows on the same hardware, so it must be the OS as that's the only differentiating factor.

Your observation on the partitioning could be a good one though, I'll give that a try.

 

[runebinder]

Okay, deleted all partitions and used Disk Utility to create a single Mac OS Journaled (Extended) partition and the results are identical, so it's not the partitioning scheme causing it.

 

[Fishrrman]

Re post 4:
- Try a different enclosure
- Try a different nvme drive
- Try a different cable

Personal experience:
I have a USB3 Gen2 enclosure with an nvme drive (a Crucial, if I remember), and it gives me reads of 965MBps with a USBc cable. This is using Mojave, however, not Catalina.

 

[Ifti]

I think its the enclosure. I've tried various external NVMe enclosures with my Mac (Catalina) and have found them to work fine. I don't think OSX 'limits' drives in any way, although I appreciate it works fine in Windows - could it be something to do with the controller chip in the enclosure and OSX?

 

[runebinder]

Could be the SSD.

My apologies, turned out your first line was the correct one.

I have a 512GB Samsung SM961 NVMe drive in my desktop so decided this morning that I'd put that in the enclosure and test once I got back from work. The results are much more in line with what I expected.

So it must be something about the Psion controller that macOS does not like. I did read that Sabrent have done something weird in that it uses 4K sectors and no 512 Byte emulation meaning you can't clone them and I'm wondering if that could have something to do with the poor read speed.

They have a drive tool kit that lets you change to 512, unfortunately my Desktop is failing to boot to Windows whilst it is in the enclosure, and the tool kit doesn't recognise the Sabrent drive when it's in the enclosure. Got an old Z170 mobo that only has one M.2 slot so it would appear that I'm in a bit of a catch 22 situation.

Think I'll use the Sabrent as the boot drive on the PC as I know it works fine with Windows, and then use my SM961 for the external. Not the storage size I wanted but at least I gain the speed and the PC gets an extra 1.5TB.
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I think its the enclosure. I've tried various external NVMe enclosures with my Mac (Catalina) and have found them to work fine. I don't think OSX 'limits' drives in any way, although I appreciate it works fine in Windows - could it be something to do with the controller chip in the enclosure and OSX?

It's the Sabrent SSD unfortunately.

 

[naerct]

That's great speeds for a device that maxes out at 1GB/s. You also reinforced my inclination to buy only Samsung blades. I've used several of their blades inside a 12-core cMP with a bifurcation PCI card where I get reads of 2.8GB/s for the 970 and 2.4 for the 960. These were both EVOs. But I also installed a 970 PRO in a similar setup on a 4-core cMP, and his PRO was the same as my EVO. I also installed an external boot using a 970 EVO+ on a USB3 iMac, as the spinner inside was painfully slow from being too full. This is her office computer which is used by several other people. Obviously your 3.1 gen2 is twice as good as the reads and writes averaged about 450MB/s. That's about the same as a good SATA SSD from USB3, but will double in speed with her next office computer 3.1 gen2, or she can use it was a fast portable for her big i7 iMac in her studio. The external enclosure is really tiny, and very rugged, perfect for getting an extra copy of imagery from a remote, tethered shoot.

 

[runebinder]

That's great speeds for a device that maxes out at 1GB/s. You also reinforced my inclination to buy only Samsung blades. I've used several of their blades inside a 12-core cMP with a bifurcation PCI card where I get reads of 2.8GB/s for the 970 and 2.4 for the 960. These were both EVOs. But I also installed a 970 PRO in a similar setup on a 4-core cMP, and his PRO was the same as my EVO. I also installed an external boot using a 970 EVO+ on a USB3 iMac, as the spinner inside was painfully slow from being too full. This is her office computer which is used by several other people. Obviously your 3.1 gen2 is twice as good as the reads and writes averaged about 450MB/s. That's about the same as a good SATA SSD from USB3, but will double in speed with her next office computer 3.1 gen2, or she can use it was a fast portable for her big i7 iMac in her studio. The external enclosure is really tiny, and very rugged, perfect for getting an extra copy of imagery from a remote, tethered shoot.

At some point I'll swap it for a larger capacity drive, it'll be a Samsung.

Installed Windows fresh on the Sabrent and was able to run the toolkit, no available firmware updates and it's already set to 512B sectors so it's a drive that doesn't play nicely with macOS. On the plus side it means I won't have the cloning issues I was reading about online when it's set to 4K sectors.

 

[JosePDR]

Hello, I just registered to put in my two cents in this post.

I am having exactly the same issue. In my case is a TDBT enclosure with an WD SN750 500gb. I did a speed test brand new and was perfect with the 1000gb/s. Then I did the Boot camp install also, and since then I'm having the same results.

In windows is perfect, but in Mac is capped to 100mb tops.

I reached to the manufacturer of the enclosure and we are trying to figure it out.

I would say that it is indeed a Mac Catalina problem with the partition structure of the nvme necesary for the boot camp install.

 

[sdedalus1]

Jeyi i9 GTR USB 3.1 enclosure (RealTek RTL9210 controller)
Sabrent Rocket 1TB, formatted GUID, HFS+ (Journaled)
Catalina 10.15.6

Just chiming in to say I'm having the same problem, judging from both Blackmagic Disk Speed Test and AJA System Test. After a few GB of disk activity, reads occasionally drop to 150–200 MB/s before climbing back up to max over a few seconds, then after more activity, stays low. The drive was fast when it was installed (with Sintech adapter) inside a 2014 MBP.

An exFAT partition on the same drive only partly shows the slowdown: the Blackmagic test shows a slowed read speed on the first run, but then full read speeds (~ 900 MB/s) on subsequent runs; whereas AJA shows slowed read over multiple runs, similar to HFS+.

Strangely, Amorphous Disk Mark doesn't show the problem on HFS+ (500 MB Seq QD4 = > 900 MB/s read & write) but does show it on exFAT (500 MB Seq QD4 = 200 MB/s read & 450 MB/s write).

I guess I'm glad to hear it's not the enclosure, but is there a software fix for this? Could it be both speed tests are off? Amorphous shows the opposite situation as the others (slower on exFAT, not on HPFS+). Should we be filing bug reports with Apple? What's another reliable test for read speeds?

I would rather not format the drive as exFAT (not journaled, I've read complaints of corruption) or NTFS.

 

[freakyterrorist]

Having the same issue. M1 Mac Mini, External NVME enclosure with Realtek RTL9210 controller and Crucial P1 1TB NVME SSD.
Black Magic shows 900MBps writes but only 200MBps reads. Drive is formatted NTFS and mounted using paragon driver.

Spoiler: System Report

TL9210:





Product ID: 0x9210


Vendor ID: 0x0bda (Realtek Semiconductor Corp.)


Version: 31.00


Serial Number: 012345678939


Speed: Up to 10 Gb/s


Manufacturer: Realtek


Location ID: 0x01200000 / 1


Current Available (mA): 900


Current Required (mA): 896


Extra Operating Current (mA): 0