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Ok, so, while we're on the topic, here's a fun question I've never been able to wrap my brain around: How [with volume encryption] does the drive ever know what's free and what isn't [for Trim and garbage collection]? Doesn't every block appear to be in use 100% of the time if it's encrypted at the volume level, or if the drive has ever been full? ...
 


Ric Ford

MacInTouch
Ok, so, while we're on the topic, here's a fun question I've never been able to wrap my brain around: How [with volume encryption] does the drive ever know what's free and what isn't [for Trim and garbage collection]? Doesn't every block appear to be in use 100% of the time if it's encrypted at the volume level, or if the drive has ever been full? ...
As I understand it, volume encryption is at a lower level than file-system operations, such as file deletions and Trim. So, to the file system, nothing changes between FileVault-encrypted and non-encrypted (and T2-encrypted) volumes. Apps and the OS still read, write, delete and trim blocks in all cases. Blocks are encrypted en-route and decrypted on return, invisibly to apps and the file system, which work with the unencrypted data. The SSD controller doesn’t need to know or care what’s in the blocks; they’re just sets of bytes to be stored, retrieved, or erased, each at a particular location, whatever their contents happen to be.*

FileVault 2/CoreStorage is based on logical volume management. See:

(*Some Sandforce controllers have done unique, tricky compression processing, which has special issues. OWC used and evangelized these extensively.)
 


How [with volume encryption] does the drive ever know what's free and what isn't [for Trim and garbage collection]? Doesn't every block appear to be in use 100% of the time if it's encrypted at the volume level, or if the drive has ever been full?
... FileVault 2/CoreStorage is based on logical volume management. See...
It will, of course, depend on how the encryption system is implemented.

If it's implemented like an encrypted disk image (i.e. as one giant file), then Trim probably can't work, because freed blocks will be indistinguishable from in-use blocks, and the ecncrypted logical blocks may not even align with the device's logical blocks (especially if there is also data compression involved).

If, on the other hand, each block is separately encrypted, or if the algorithm makes certain that each encrypted block corresponds to exactly one logical block, then Trim can still be used. (It might sacrifice some amount of privacy, because freed blocks will probably read back as all zeros instead of as random bits, but only the most paranoid people should consider that a significant breach.)
 


Ric Ford

MacInTouch
I don't remember seeing this back in May, but it's worth noting a Mac compatibility issue with the Samsung 970 EVO Plus SSD (which doesn't affect the plain Samsung 960 EVO version).
BartechTV said:
Samsung releases new firmware for 970 EVO Plus that resolves macOS compatibility issues
Samsung today released a new firmware update for the 970 EVO Plus NVMe SSD that resolves compatibility problems when using the drive under macOS.

Previously, while the original 970 EVO worked without issues, the 970 EVO Plus would cause regular kernel panics under macOS, followed immediately by a spontaneous reboot. With the new firmware installed, the 970 EVO Plus works flawlessly under both macOS and Windows, with speeds around the 3000MB/s mark.
 


Reading this article on SSDs, it appears that the move to quad- and quintuple-density SSDs comes with a cost: speed and, potentially, reliability. Bottom line (in my opinion): this rush to increase density will come at a cost that will be when these "cheap" drives start to fail prematurely....
 


Reading this article on SSDs, it appears that the move to quad- and quintuple-density SSDs comes with a cost: speed and, potentially, reliability. Bottom line (in my opinion): this rush to increase density will come at a cost that will be when these "cheap" drives start to fail prematurely....
Thank you, Barry. Yes, besides the higher failure rate, it seems like these PLC SSDs will be running like regular 7200-rpm hard drive read/write speeds. Just hope Apple doesn't consider using them.
 


It will, of course, depend on how the encryption system is implemented.
If it's implemented like an encrypted disk image (i.e. as one giant file), then Trim probably can't work [...] If, on the other hand, each block is separately encrypted, or if the algorithm makes certain that each encrypted block corresponds to exactly one logical block, then Trim can still be used.
No need to guess, some helpful people at the University of Cambridge have figured it all out for you.

As a general matter, full disk encryption systems virtually always work at the block level for multiple reasons - because disks and SSDs are intrinsically block-level devices, to take advantage of block ciphers, and so that mechanisms like block caches and Trim can still be supported. Basically, as Ric suggested a few posts above, the data path just encrypts and decrypts blocks as they fly by - all of the complexity is in the key management.
 


I don't remember seeing this back in May, but it's worth noting a Mac compatibility issue with the Samsung 970 EVO Plus SSD (which doesn't affect the plain Samsung 960 EVO version).
True. I run one of these drives on my Hackintosh, and initially there were many reports of flaky operation and crashes. Samsung does make a Linux-based bootable disk image that you can download, burn to a CD, then boot from to update the firmware. This was some months ago, so I'd imagine drives currently on the market have the new firmware by now.
 


Ric Ford

MacInTouch
AnandTech has a review of a new Thunderbolt 3 SSD and previously covered the Samsung X5:
Ganesh T S said:
OWC Envoy Pro EX Thunderbolt 3 and Plugable TBT3-NVME2TB Portable SSDs Review
... In summary, we would have liked better performance consistency for stressful writes from both the Plugable TBT3-NVME2TB and the OWC Envoy Pro EX Thunderbolt 3. However, given the price points, very few users may complain about that aspect. The thermal design for the Plugable drive is excellent, while the ruggedness of the OWC drive may make it attractive to certain market segments. By and large, the performance of the Plugable and OWC drives are equivalent, and users can make a purchase decision purely based on the best available deal at the time of purchase. On a general note, we are happy to see the appearance of economical Thunderbolt 3 SSDs in the market with high performance for real-world workloads.

The Samsung Portable SSD X5 Review - Thunderbolt 3 and NVMe in a Premium Enclosure
... Consumers would be prudent to treat the X5 as a premium product - it performs admirably for the vast majority. However, for power users who frequently transfer 100s of gigabytes in one go, a solution like our DIY Thunderbolt 3 SSD is a better choice. Our DIY device does not look as sleek as the X5, but, it is cheaper and has more consistent performance.
Amazon links:
 


It's been a long time since I invoked TRIM on my SSDs. I think it was in Sierra that I invoked it. Has anything changed since then? I also forgot the Terminal command to invoke TRIM. I don't know if any websites have been updated for Catalina. Is it still possible to invoke TRIM in Catalina and what is the Terminal command for TRIM? Thank you.
 


Ric Ford

MacInTouch
It's been a long time since I invoked TRIM on my SSDs. I think it was in Sierra that I invoked it. Has anything changed since then? I also forgot the Terminal command to invoke TRIM. I don't know if any websites have been updated for Catalina. Is it still possible to invoke TRIM in Catalina and what is the Terminal command for TRIM? Thank you.
If it's an Apple SSD, you only have to worry about a few Apple defects (for which Apple has provided repair programs and software updates), not about "invoking" Trim, which is done automatically.

For third-party SSDs, the simplest thing is to just get Disk Sensei, which will help you manage Trim (and more).
 


... I also forgot the Terminal command to invoke TRIM. I don't know if any websites have been updated for Catalina. Is it still possible to invoke TRIM in Catalina and what is the Terminal command for TRIM?
... For third-party SSDs, the simplest thing is to just get Disk Sensei, which will help you manage Trim (and more).
My Trim Tools apps will do the job. Free. I just wrote the AppleScript wrappers. They work.
 


It's been a long time since I invoked TRIM on my SSDs. I think it was in Sierra that I invoked it. Has anything changed since then? I also forgot the Terminal command to invoke TRIM. I don't know if any websites have been updated for Catalina. Is it still possible to invoke TRIM in Catalina and what is the Terminal command for TRIM? Thank you.
After I installed Catalina on my 2018 Mac Mini, all of my attached SSDs (four in my Akitio Thunder3 Quad X) had TRIM disabled.

A simple Terminal command
Bash:
sudo trimforce enable
and a reboot had all of them TRIM-enabled again.
 



The SSD that has Catalina installed is a Samsung SSD. I think Barry and Tony's advice is perfect. I will remember Ric's suggestion. If there is any other advice, I'll read it before I commit. Thank you.
 



Ric Ford

MacInTouch
There is currently a sale on Amazon.com for a Samsung T5 1TB External SSD.
Samsung T5 Portable SSD - 1TB - USB 3.1 External SSD - $137.99
According to camelcamelcamel, this is the lowest price seen to date on Amazon.
Amazon has a Sandisk 1TB external SSD for even less, $124.99:
I personally prefer spending the small premium for the Samsung T5, because
  • it's smaller and has an aluminum case,
  • it has a nice activity indicator light,
  • it has two good cables (USB-C and USB Type A) instead of an adapter that may be glitchy, and
  • I haven't had any problems with a bunch of the T5's, but I got a defective SanDisk Extreme Portable SSD last year that I had to return to Amazon.
Of course, I recommend always testing any storage media, e.g. with SoftRAID's Certify feature, before using it for anything meaningful.

On the flip side, beware of these APFS/T2 compatibility issues with the Samsung T5:
Bombich Software said:
Help! My clone won't boot! | Carbon Copy Cloner | Bombich Software
... Some users have reported that the Samsung T5 Portable SSD cannot function at all as a bootable device on the T2-based MacBook Pro 2018. Efforts even to install macOS Mojave onto this device fail to produce a bootable volume. This is a popular enclosure that we've seen great success with, and so far these reports are limited to the 2018 MacBook Pro.

Catalina: We have received numerous reports of general bootability problems with this device on macOS Catalina.

The Samsung T5 Portable SSD (and also the Transcend StoreJet SSD) also introduces an exceptional delay during startup (on any Mac, not just T2 Macs), whether you're attempting to boot from that device or your Mac's internal hard drive. This appears to be a compatibility problem between the Mac's firmware and this particular SSD when the SSD is formatted as APFS and when the SSD has an installation of macOS (whether placed there via cloning or via the Installer). To avoid this delay, and only if your Mac is running macOS Mojave or an earlier OS, we recommend formatting these SSDs as HFS+ until the compatibility problem is resolved:
  1. Open Disk Utility
  2. Choose Show all devices from the View menu
  3. Select the top-level "parent" device of the Samsung T5 SSD in Disk Utility's sidebar
  4. Click the Erase button in the toolbar
  5. Set the format to Mac OS Extended, Journaled, set the Scheme to GUID Partition Map. and give the new volume a name
  6. Click the Erase button
  7. Open CCC and re-select the new volume as the destination, then run the backup task
Note: If you have a T2 Mac, please bear in mind that T2 Macs cannot boot from an encrypted HFS+ formatted device. The Samsung T-series devices will not be a suitable backup device for your T2-based Mac if you require that the backup disk is encrypted.
 


I personally prefer spending the small premium for the Samsung T5, because
  • it's smaller and has an aluminum case,
  • it has a nice activity indicator light,
  • it has two good cables (USB-C and USB Type A) instead of an adapter that may be glitchy, and
  • I haven't had any problems with a bunch of the T5's, but I got a defective SanDisk Extreme Portable SSD last year that I had to return to Amazon.
Just ordered one through your link. Looks like a really nice little drive. Curious to see how much it improves backup time from my 2014 iMac, which has USB 3.0 ports and macOS Sierra. I've been using a 7200-RPM mechanical drive in an OWC [enclosure] up until now. No APFS here.
 


Ric Ford

MacInTouch
My Trim Tools apps will do the job. Free. I just wrote the AppleScript wrappers. They work.
I don't know if you want to fuss any more with these – and they're a great free contribution – but I noticed two things, for what they're worth, in case you're interested in feedback / updating:
1. Error messages on open:​
"Enable TRIM.app" can't be opened because it is from an unidentified developer.
2. No apparent provision for drives other than the internal/boot drive (which isn't clearly identified).​
 


I don't know if you want to fuss any more with these – and they're a great free contribution – but I noticed two things, for what they're worth, in case you're interested in feedback / updating...
Yep, Ric, I wrote those a couple of years ago when Apple's security wasn't as rigorously enforced. Haven't spent any time on them since then.
 


I don't know if you want to fuss any more with these – and they're a great free contribution – but I noticed two things, for what they're worth, in case you're interested in feedback / updating:
1. Error messages on open:​
2. No apparent provision for drives other than the internal/boot drive (which isn't clearly identified).​
I tried one of these scripts on a Catalina install and got the error, but when I went to the Security & Privacy preference pane, it offered me an "allow" button, and sure enough, then it worked fine.
 


I personally prefer spending the small premium for the Samsung T5, because
  • it's smaller and has an aluminum case,
  • it has a nice activity indicator light,
  • it has two good cables (USB-C and USB Type A) instead of an adapter that may be glitchy, and
  • I haven't had any problems with a bunch of the T5's, but I got a defective SanDisk Extreme Portable SSD last year that I had to return to Amazon.
Of course, I recommend always testing any storage media, e.g. with SoftRAID's Certify feature, before using it for anything meaningful. On the flip side, beware of these APFS/T2 compatibility issues with the Samsung T5...
Would this be a good candidate for an external Mojave VM or boot drive when I upgrade to Catalina on my 2017 iMac?
 


Ric Ford

MacInTouch
Would this be a good candidate for an external Mojave VM or boot drive when I upgrade to Catalina on my 2017 iMac?
The Samsung T5 [Amazon] should work fine. Alternatives include the Samsung X5 [Amazon], a Thunderbolt 3 drive that's far faster – as fast as an internal SSD – or a simple SATA SSD (e.g. Samsung 860 EVO [Amazon]) with a USB 3 adapter or enclosure or SATA dock – clunkier but perhaps a bit cheaper and possibly better for avoiding thermal throttling (though I can't say for sure).
 


Ric Ford

MacInTouch
... On the flip side, beware of these APFS/T2 compatibility issues with the Samsung T5...
I just did a test of a 500GB Samsung T5 without turning up any problems. The SSD had an HFS+ partition holding a bootable macOS 10.13 Sierra system plus an APFS Container holding an APFS volume.
  1. I used Carbon Copy Cloner to clone a vanilla macOS 10.14 Mojave partition on a 2017 iMac 5K to the FileVault-encrypted APFS volume on the Samsung T5.
  2. Booted the Mojave system from the Samsung T5 on a 2017 MacBook Air.
  3. Booted the Mojave system from the Samsung T5 on a 2018 MacBook Pro.
 


The Samsung T5 [Amazon] should work fine. Alternatives include the Samsung X5 [Amazon], a Thunderbolt 3 drive that's far faster – as fast as an internal SSD – or a simple SATA SSD (e.g. Samsung 860 EVO [Amazon]) with a USB 3 adapter or enclosure or SATA dock – clunkier but perhaps a bit cheaper and possibly better for avoiding thermal throttling (though I can't say for sure).
I’d really love to go Thunderbolt 3, but now you’re talking ~$300!
 




The Samsung T5 [Amazon] should work fine. Alternatives include the Samsung X5 [Amazon], a Thunderbolt 3 drive that's far faster – as fast as an internal SSD – or a simple SATA SSD (e.g. Samsung 860 EVO [Amazon]) with a USB 3 adapter or enclosure or SATA dock – clunkier but perhaps a bit cheaper and possibly better for avoiding thermal throttling (though I can't say for sure).
... An equally excellent external drive is OWC's Envoy Pro EX [Amazon link], which is a various sized internal NVMe SSD inside their Thunderbolt 3 enclosure. On a 2017 iMac 5K using that as an external boot drive, and using BlackMagic to test the speeds, I have seen some incredible read and write speeds (2373 MB/s read and 1923 MB/s write).
 


Ric Ford

MacInTouch
... An equally excellent external drive is OWC's Envoy Pro EX
[Amazon link], which is a various sized internal NVMe SSD inside their Thunderbolt 3 enclosure. On a 2017 iMac 5K using that as an external boot drive, and using BlackMagic to test the speeds, I have seen some incredible read and write speeds (2373 MB/s read and 1923 MB/s write).
That competes with the Samsung X5, which I benchmarked at even higher speeds. The Envoy Pro EX has a captive Thunderbolt 3 cable, while the Samsung X5 has a Thunderbolt 3 port and a separate cable. On Amazon at the moment, the Envoy Pro EX is priced the same for 500 GB but is far less for 2 TB and looks reasonable at $280 for 1 TB.
 



That competes with the Samsung X5, which I benchmarked at even higher speeds. The Envoy Pro EX has a captive Thunderbolt 3 cable, while the Samsung X5 has a Thunderbolt 3 port and a separate cable. On Amazon at the moment, the Envoy Pro EX is priced the same for 500 GB but is far less for 2 TB and looks reasonable at $280 for 1 TB.
Hmmm, interesting, Ric. The captive cable on the Envoy Pro has always bothered me. And the price difference is negated somewhat by the X5's Thunderbolt 3 port. I might have to take a look at that. Thanks!
 




That competes with the Samsung X5, which I benchmarked at even higher speeds. The Envoy Pro EX has a captive Thunderbolt 3 cable, while the Samsung X5 has a Thunderbolt 3 port and a separate cable. On Amazon at the moment, the Envoy Pro EX is priced the same for 500 GB but is far less for 2 TB and looks reasonable at $280 for 1 TB.
The Samsung X5 is no longer available direct from Amazon. Other sellers have them starting at $349.
 



Ric Ford

MacInTouch
Confusingly there are two versions of the Envoy Pro EX....
OWC's product naming is absurdly confusing to say the least, recycling the same name for completely different device types with unique, incompatible interfaces (e.g. Thunderbolt 3 vs. USB 3). Here's what I posted on the MacInTouch home page (product section) a while back:
Envoy Pro EX is a confusing collection of compact SSD storage devices from Other World Computing Inc. that range from a 5Gbps USB 3.0 drive at the low end to 10Gbps USB-C M.2 NVMe devices in the middle then 40Gbps Thunderbolt 3 models at the high end. Shared features include an aluminum enclosure and bus-powered operation (no external power supply needed). An enclosure-only USB-C model lets you add your own NVMe SSD, and there is a choice of capacities among the other models.
Envoy Pro EX models range from $89 (250GB USB) up to $829 (2TB Thunderbolt 3) for macOS 10.13 and up. Note the company's warning about a Thunderbolt bug in Apple's new Mac Mini computers:

Mac mini (2018) Users ONLY: Bus-powered Thunderbolt 3 solutions like the Envoy Pro EX may experience intermittent disconnects when attached directly to one of the Thunderbolt 3 ports on the Mac mini. To avoid this issue, we recommend connecting your Envoy Pro EX through another wall-powered Thunderbolt 3 device in a daisy-chain. These intermittent disconnects only occur when connected directly to the Mac mini (2018) and are not seen on other computer models. This issue has been reported to Apple for resolution.
Critical compatibility issues:

Thunderbolt 3 and USB-C ports look the same but aren't. You can use a USB-C device with a Thunderbolt 3/USB-C port, but you cannot use a Thunderbolt 3 device with any USB-only (non-Thunderbolt) port, even if a connector or adapter fits.​
You cannot use a non-powered Thunderbolt 3 device — e.g. Samsung X5 or Envoy Pro EX — with an older Mac's Thunderbolt or Thunderbolt 2 port, even with a Thunderbolt 3-to-Thunderbolt 2 adapter — it simply won't work all by itself.​
You can use such a non-powered Thunderbolt 3 device with an older Mac, however, only by connecting it to a powered Thunderbolt 3 dock that you then connect via the Thunderbolt 3-Thunderbolt 2 adapter and Thunderbolt 2 cable to the older Mac's Thunderbolt/Thunderbolt 2 port.​
 


You cannot use a non-powered Thunderbolt 3 device — e.g. Samsung X5 or Envoy Pro EX — with an older Mac's Thunderbolt or Thunderbolt 2 port, even with a Thunderbolt 3-to-Thunderbolt 2 adapter — it simply won't work all by itself.
You can use such a non-powered Thunderbolt 3 device with an older Mac, however, only by connecting it to a powered Thunderbolt 3 dock that you then connect via the Thunderbolt 3-Thunderbolt 2 adapter and Thunderbolt 2 cable to the older Mac's Thunderbolt/Thunderbolt 2 port.
Now I know what my clients feel like. {head-banging} :D

(And I know Ric's explanation is as simple as it could be.)
 



Meanwhile I am looking for an external enclosure or PCI card which will hold two removed Mac SSDs. Each is 256GB and are kinda useless individually. Bonus points for making them look like a single drive to the Mac it is attached to.
 



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