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As of OS X 10.10, Apple uses kext signing. Ever since it has become difficult and dangerous to manually activate TRIM for third-party SSDs on OS X. That means users with non-Apple SSDs will sooner or later see degrading write speeds.

So I am wondering what are my options to avoid this situation. Some approaches I could think of imply additional problems:

  • Are you aware of any alternative approach, that does not require disabling kext signing?
  • Are there tools or tricks to manually clean up a SSD (i.e. issue a TRIM command)?
  • If I decided to temporarily use a tool like TRIM Enabler how long would it need to be activated, in order to clean the disk?

To summarize: No TRIM on Yosemite. What can I do?

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  • What SSD is connected to which Mac? I'm putting this on hold for a bit to see if you can explain more about what your issue is as opposed to looking for general discussion on multiple questions. (It's probably too broad as well as off-topic) as written.
    – bmike ♦
    May 4, 2015 at 18:58
  • @bmike Better? Do you think I should delete the sub-questions in the list?
    – n1000
    May 4, 2015 at 19:31
  • Yes - but the title might need a rephrase. Are you simply asking for a software recommendation on Trim Enablers that are signed? The "in shape" part is vague and the three bullets make this more like three separate questions. I'd be keen to know how you are measuring speeds rather than asking for "potential snake oil" to prevent something that's theoretical and not measurable / happening.
    – bmike ♦
    May 4, 2015 at 19:34

5 Answers 5

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EDIT 3:

Yes! Since the release of 10.10.4, Apple now provides a new tool called trimforce, allowing users to activate TRIM also on unsupported disks. So now the ultimate and final answer is: 

sudo trimforce enable

/EDIT 3

EDIT 1:

Finally I found a way! Apparently there is a neat trick hidden in the fsck tool as this answer says.

So in the future I will boot into Single User Mode (press ⌘+S at boot screen) from time to time and issue the command fsck -fy. It will check the disk and finish with the message Trimming unused blocks.

/EDIT 1

EDIT 2:

So there is a new tool called Disk Sensei that specializes on exactly that problem. It has a manual TRIM command and helps you turning Yosemite's kext signing on and off.

/EDIT 2:

Furthermore, I read about DiskFresh which would somewhat accomplish what I was originally asking for. This Windows (Bootcamp partition required) tool will rewrite all data of partitions or an entire disk. This approach seems a little less painful than wiping my SSD and restoring it from a backup. However, it also comes with the downside of doing an additional write cycle.

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Alternative approach would be to leave as much space on SSD free as possible for GC to work well.

I did this i.e. enabled TRIM on clients computer just when Yosemite was released and I didn't fully understand consequences of it. Now I only hope she will install update with new AppleAHCIBlockStorage before she will try cmd+optn+p+r for some reason.

Now I wouldn't do it on anything except your computer that you can deal with being down for some time if you clear NVRAM. You had to have another Mac or boot media/install media around and printout of sudo nvram boot-args=kext-dev-mode=1 though.

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    What GC are you talking about? I think you're conflating two different things.
    – John Schmitt
    Jan 3, 2015 at 22:08
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    @JohnSchmitt “GC” is another function of SSDs to ensure durability and performance. Unlike TRIM, it works completely internally to the drive, so there is no need for OS X to support it for it to be enabled in a non-Apple SSD. It is distinct from TRIM and complementary to it. A sophisticated GC algorithm cannot replace TRIM because it works at a different level, but it can contribute to preserve the SSD's performance even without TRIM. It works better when the disk isn't full (what this answer is saying).
    – Pascal Cuoq
    Jan 3, 2015 at 22:23
  • More reading on TRIM vs. GC: cindori.org/trim-vs-garbage-collection
    – n1000
    May 25, 2015 at 13:00
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Depending on the SSD manufacturer, I've read that restarting your machine and holding down the option key, which will bring you to the start-up disk chooser and then letting it sit in that state for a few hours without choosing a boot disk will allow garbage collection to commence, I believe I read that on the MacObserver's MacGeekGab or maybe it was the podcast, not sure. Have you heard this to be true? @PascalCouq

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  • This is indeed true for some drives. For example the M500. I just revived a 960GB M500 last night after I also updated the firmware. Left it unbooted but running for 8 hours, with no work on it so truly idle and it was fully restored from 16mb/s reads and writes to 400+mb/s. Had it for 2 years. It's important to note that GC and trim are not exclusive processes.
    – MiB
    Feb 9, 2017 at 23:50
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You might want to try the software "disktester." It has a recondition function that apparently works with SSDs. I haven't yet tried it myself, but it looks pretty legit.

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  • I tink reconditioning will make you lose all your date.
    – Vincent
    May 4, 2015 at 19:13
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I recommend enabling trim and doing firmware updates! :)

results from enabling trim and updating firmware

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