hoakley April 14, 2023 Macs, Technology

Will your new SSD support TRIM and SMART?

While Mints can now tell you whether your expensive new SSD gets trimmed by your Mac when it’s mounted, you really want to know which features are supported by different SSDs before you pay for them. With the aid of a couple of Macs, one Intel T2 and the other Apple silicon, over a dozen assorted SSDs, and the occasional kernel panic, I can now present my conclusions, as of macOS Ventura 13.3.1.

As far as your Mac is concerned, each external SSD has three important properties:

the SSD itself, e.g. Samsung 990 PRO,
the bus interface of the SSD, either SATA or NVMe,
the connection to the Mac, either USB or Thunderbolt.

The SSD

All reasonably recent, better quality SSDs should support the TRIM command or an equivalent, garbage collection, and SMART health indicators. Manufacturers should provide this information, although it can sometimes be hard to find. What few reveal is how these are implemented, and the level of support for different SMART indicators.

If you’re unable to satisfy yourself that the SSD has adequate support for these, then don’t buy that brand or model.

Bus interface

This is important for SSDs used with Macs, as it determines whether macOS recognises them as having TRIM support, and whether it will obtain and monitor SMART health indicators.

SSDs with a SATA interface don’t enjoy TRIM support as standard, and only provide limited SMART support when they’re connected by Thunderbolt, and none via USB. Over Thunderbolt, their SMART support is limited, in that Disk Utility reports their verification, diskutil gives no detailed information, but dedicated apps like DriveDx should be able to provide a useful range of health indicators. If you have to use SATA SSDs, then putting them into a Thunderbolt enclosure like an OWC ThunderBay 4 does at least provide some SMART access, although it still doesn’t enable TRIM support.

NVMe SSDs are better off, as they appear to enjoy TRIM support whether they’re connected by USB or Thunderbolt, although they only have SMART support when connected by Thunderbolt. As the SATSMART kernel extension only supports SATA and not NVMe, there’s currently no way to gain access to SMART indicators for NVMe SSDs connected by USB.

Connection

By default, no SSDs connected by USB have SMART support, and only NVMe SSDs can support TRIM. SMART support can be added for SATA SSDs using the SATSMART kernel extension, but on Apple silicon Macs that requires reduced security.

A Thunderbolt connection should provide NVMe SSDs with full support for both TRIM and SMART, but for SATA SSDs TRIM still isn’t supported, and SMART indicators are more limited.

System Information

The current version of System Information is confusing and incomplete when it comes to TRIM support:

SATA SSDs connected via Thunderbolt have TRIM support listed in the SATA section.
NVMe SSDs connected via Thunderbolt have TRIM support listed in the NVMExpress section.
All SSDs connected via USB should have TRIM support listed in the USB section, but don’t.

Where System Information does report that TRIM is supported, this matches reports in the log by APFS of trimming SSDs when mounting them.

Support levels

If you want an SSD to have full TRIM and SMART support, the only suitable combination is:

an SSD with good TRIM and SMART support,
an NVMe interface,
a Thunderbolt connection.

You may also be able to attain that for a suitable SSD with a SATA interface over USB if you:

use trimforce to enable TRIM to external SSDs,
install the SATSMART kernel extension to enable SMART support.

Before considering enabling trimforce, ensure that you read its man page.

One popular combination can’t offer SMART support under any circumstances, but should support TRIM without the use of trimforce: an NVMe interface with a USB connection. These are typically USB 3.1 Gen 2 models claiming transfer speeds in excess of 600 MB/s.

13Comments

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1

Enzo Vincenzo on April 14, 2023 at 7:31 am
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Dear Howard, this is really a detailed synthesis like a drawing or a painting by Leonardo in an ingenious and artistic scheme by Mondrian. You have provided a complete and perfect description in an appropriate summary. Great! A thousand thanks!

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- 2
  
  hoakley on April 14, 2023 at 1:03 pm
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  Thank you.
  Howard.
  
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3

Dandu on April 14, 2023 at 12:53 pm
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Hi. Actually, it’s possible to have TRIM with a SATA SSD connected in USB.

It works with many enclosure, but not all : https://www.journaldulapin.com/2021/12/24/trim-usb-monterey/

It’s complicated to find the information, but many recent bridge can do that. The problem is the bridge used, and the firmware. The enclosure must use UASP and transfer the TRIM command, but it’s not common.

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- 4
  
  hoakley on April 14, 2023 at 1:02 pm
  Reply
  
  Thank you.
  You omitted mentioning that you have to use the trimforce command to enable it (as detailed in that link), which is exactly what I have written above. But without enabling that, I don’t see any evidence that any SATA-USB SSD will trim in Ventura.
  And as I have written above, before enabling trimforce you should read its man page, for important warnings and cautions.
  Howard.
  
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5

EcleX on April 14, 2023 at 1:25 pm
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Thanks for the useful information.

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6

Simon on April 14, 2023 at 1:44 pm
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Excellent summary. Thank you, Sir.

Decent NVMe-USB enclosures run $20. While the least expensive TB shell I know for NVMe is the OWV Envoy Express TB3 which is $90. $70 is a significant difference for SMART.

On a TM backup SSD the difference from TRIM is likely not justified because performance is throttled by macOS anyway. (and ~500 Mbps from SATA-USB is fine for TM)

If you want performance, you’re going to get NVMe. And if you’re really worried about best performance, TB3/4 is a must, not just because of TRIM. But then you’re also going to want something like a Samsung 970EVOPlus/980PRO to really exploit TB3/4’s real-world ~3 GB/s bandwidth. At 2TB that’s a $140/$150 drive. Problem then is, the case should probably offer active cooling or else the SSD could throttle during prolonged use. And that’s no longer a $90 shell.

Anyway, those Samsungs are incidentally also $60 more than a much cheaper eg. Intel 670p at $85 for 2GB. This drive will still saturate the 10 Gbps you get from the Mac’s USB3, but it won’t be able to fully exhaust TB’s ~32 Gbps. So cooling not required, and you might as well resort to a USB 3.2 shell, but then again, no SMART.

Nobody said this was easy. :))

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- 7
  
  hoakley on April 14, 2023 at 2:18 pm
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  Thank you.
  One other thing to bear in mind is that, unlike hard disks, you should expect a working life of up to ten years. So a more costly investment now should still prove useful when we’re on even faster speeds in the future.
  Howard.
  
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8

Duncan on April 14, 2023 at 3:33 pm
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When I read this…

As far as your Mac is concerned, each external SSD has three important properties:

* the SSD itself, e.g. Samsung 990 PRO,
* the bus interface of the SSD, either SATA or NVMe,
* the connection to the Mac, either USB or Thunderbolt.

… all these different variables floating around distilled down to a clear picture of all the possibilities. That was an excellent way of expressing the complexity.

A different dimension in this discussion includes the status of TRIM and SMART support (with variable levels of SMART reporting available), so with some clever graphical layout I imagine all combinations could be displayed on a chart of some sort.

(In an idealized, fantasy world, such a chart would be standardized, and the data for each model of drive available could be crowd-sourced and entered into a master database, similar to how nutritional information is printed on product packaging [at least in the US]. Of course it would be better if the manufacturers themselves provided the data themselves, but we know how that tends to go.)

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- 9
  
  kapitainsky on April 14, 2023 at 5:54 pm
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  Isn’t it why we love our macs computers? Somebody did all hard job to get all pieces to work in tune. It is not open system – for good or bad. I love it as my laptop but would never use for server. I accept limitations and I tried alternatives e.g. trying to use Linux as workstation – back to Apple:) And at the end anybody spending money on Apple and hoping for Linux freedom is disillusioned. It is what this company is doing.
  
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  - 10
    
    hoakley on April 14, 2023 at 8:48 pm
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    I agree: macOS server was discontinued some years ago for good reasons. I still have an Xserve upstairs, but haven’t used it for years.
    Howard.
    
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- 11
  
  hoakley on April 14, 2023 at 8:40 pm
  Reply
  
  Thank you.
  I did think of a chart or table, but in the end it really resolves to the two combinations in my conclusions. Intermediates lose out one way or the other.
  I’d dearly love to build in more detail, but this has already involved a couple of thousand pounds of SSDs and enclosures!
  Howard.
  
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12

Brian on April 14, 2023 at 5:53 pm
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Thanks for the insights Howard. My storage needs have been met with large enterprise hard drives, but it’s probably time to replace them after 5 years now with multiple, standalone NVMe SSDs.

With the 10 year longevity you estimated over hard disks, would that apply to NVMe of any size (2TB vs 8TB), with or without a fan in the case? The fanless OWC Envoy Express seems like a good NVMe option I guess, if lack of a fan is safe long-term? Probably okay for an offline data backup drive, but I’m not sure about an always-mounted active drive.

Is it safe to fill non-OS SSDs past 80% or 90% for data backups and general use, since there’s no OS cache on those? Thank you.

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- 13
  
  hoakley on April 14, 2023 at 8:47 pm
  Reply
  
  Thank you.
  Yes, as far as I’m aware, unless you really thrash an SSD, decent quality models should last for around ten years. I’m beginning to suspect that thermal issues are overplayed: yes, they do get warm, but the temperatures I’m seeing in normal use are fine without needing active cooling. If you’re using them for heavy media work, with sustained large writes, that would be different, of course.
  For data use and not booting, I don’t see why you shouldn’t be able to fill them to more than 90%. Although APFS is dynamic, without all the caches of the Data volume you shouldn’t need to keep that much free space.
  Howard.
  
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