By n1000

2015-01-02 21:50:33 8 Comments

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?


@Esdras Lopez 2016-06-20 04:37:29

I recommend enabling trim and doing firmware updates! :)

results from enabling trim and updating firmware

@n1000 2015-04-19 18:34:21


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



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 āŒ˜+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.



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.

@Spencer 2015-05-04 18:28:49

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.

@Vincent 2015-05-04 19:13:55

I tink reconditioning will make you lose all your date.

@Todd 2015-01-04 20:51:44

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

@MiB 2017-02-09 23:50:51

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.

@iskra 2015-01-02 22:11:46

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.

@John Schmitt 2015-01-03 22:08:42

What GC are you talking about? I think you're conflating two different things.

@Pascal Cuoq 2015-01-03 22:23:53

@JohnSchmitt ā€œGCā€ 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).

@n1000 2015-05-25 13:00:42

More reading on TRIM vs. GC:

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