MacOS – 3rd-party SSDs: enabling TRIM without disabling kext signing

macosSecurityssdtrim

Before reading this long question, please note that it is mostly outdated in light of the more recent developments reflected by the top answer.

Unfortunately Apple has decided to create kext signing in Yosemite that creates issues for SSDs that require Trim support for optimal function and longevity. Whether this is vendor lock in or not, it's made upgrading a headache. If you bought a SSD that needs trim support (at time of writing, all SSDs benefit) such as the Samsung 840 Evo, there are many reported issues when performing PRAM reset and potential future system update conflicts in addition to the current security tradeoffs (see below). Trim Enabler author says using Trim Enabler by turning off kext signing is cracking a walnut with a sledgehammer.

I'm hoping for strategy / options to work with SSDs that recommend or require Trim support. So far, because of this article, I'm considering a SSD with Sandforce or equivalent active garbage collection. I'm also considering turning on Trim Enabler periodically, then off and reenabling kext-signing to avoid issues with until (if) Apple restores TRIM support to hardware and software devs.

Please detail working hardware/software configurations and strategy/schedule as well as outcomes.

tl;dr —

Some background:

3rd party SSDs for the most part don't have trim support in Yosemite without kext signing security tradeoffs. Apple changed kext signing in OS X 10.10 such that kext singing must be disabled to use applications like Trim Enabler for trim support. So choices using Yosemite are, reduced security and potential system update issues; or, a SSD that doesn't require Trim support.

Yosemite kills third-party SSD support. This is not relevant if you're using an Apple installed SSD or SSD that doesn't require 3rd party trim support for optimal function. So, if you're using a DIY SSD, Trim support is tricky in Yosemite because of recent modifications to kext security management that affects Trim support. More about Trim Enabler for Mac:

About Trim in Yosemite In OS X 10.10 (Yosemite),

Apple has introduced a new security requirement called kext signing. (A kext is
a kernel extension, or a driver, in Mac OS X)

Kext signing basically works by checking if all the drivers in the
system are unaltered by a third party, or approved by Apple. If they
have been modified, Yosemite will no longer load the driver. This is a
means of enforcing security, but also a way for Apple to control what
hardware that third party developers can release OS X support for.

Since Trim Enabler works by unlocking the Trim driver for 3rd party
SSD’s, this security setting prevents Trim Enabler to enable Trim on
Yosemite.

To continue to use Trim Enabler and continue to get Trim for your
third party SSD, you first need to disable the kext signing security
setting.

It is important to note that the kext-signing setting is global, if
you disable it you should be careful to only install system drivers
from sources that you trust.

Best Answer

See my answer here:

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 you can do:

sudo trimforce enable

Related Solutions

MacOS – How does TRIM Enabler work

The Trim Enabler patches the following Kext-File

/System/Library/Extensions/IOAHCIFamily.kext/Contents/PlugIns/IOAHCIBlockStorage.kext/Contents/MacOS/IOAHCIBlockStorage

which checks if the ssd is a 3rd-party or Apple Branded SSD:

IOAHCI hex/ascii view

you can also enable trim manually by looking for all 'Apple' occurrences in the file and patching them in a hex-editor or via terminal:

##1. Backup old file
    $sudo cp /System/Library/Extensions/IOAHCIFamily.kext/Contents/PlugIns/IOAHCIBlockStorage.kext/Contents/MacOS/IOAHCIBlockStorage
/System/Library/Extensions/IOAHCIFamily.kext/Contents/PlugIns/IOAHCIBlockStorage.kext/Contents/MacOS/IOAHCIBlockStorage.original

##2. Patch the file to enable TRIM support
    $sudo perl -pi -e 's|(\x52\x6F\x74\x61\x74\x69\x6F\x6E\x61\x6C\x00{1,20})[^\x00]{9}(\x00{1,20}\x51)|$1\x00\x00\x00\x00\x00\x00\x00\x00\x00$2|sg' /System/Library/Extensions/IOAHCIFamily.kext/Contents/PlugIns/IOAHCIBlockStorage.kext/Contents/MacOS/IOAHCIBlockStorage

##3. Clear the system kernel extension cache

   $sudo kextcache -system-prelinked-kernel

   $sudo kextcache -system-caches

MacOS – Does OS X sometimes run a lesser-known TRIM routine with drives that are not explicitly supported

So, by virtue of:

this question is not about third party TRIM Enabler and the like

This cannot be the "right answer" it would seem. But even if thats not what the question is about, that is what the, um, "correct answer" is kind of about? So I'll give it a shot anyway...

The short answer to the title question: in short, no.

There is only one implementation... per supported controller.

hfs_unmap_free_ext doesn't refer to the hfs_unmap_free extent function.

It refers to the kext which does the "hfs_unmap_freeing."

The error,

hfs_unmap_free_ext: ignoring trim can occur for one or both of two reasons:

The drive is one that uses a supported controller, but has not been "blessed" with an Apple serial number and firmware. In this case, patching this protection out the kernel extension - what Trim Enabler does - will enable TRIM since the hardware has a driver which supports it.

(Also, myself, I would consider patching the kernel to be almost the definition of something intergral to the operating system.)
It is ignored because although the device advertises that it supports TRIM, there's no TRIM driver in the kernel for that controller, since Apple never shipped a drive based on that controller in the first place. So it just uses generic ATA commands.

(This is probably the case with your drive, due to the "not recognized as an SSD" bit.)

While:

they have programmed in nanosecond-critical timing loops that match perfectly with the access timings of the controllers used in Apple’s SSDs

is a true statement, that's definitely not why Apple locks drives. They do that so you can't get in-warranty support for a third party drive.

Apple doesn't make drives; but if you read up how Tim Cook (while COO) cornered the Asian NAND flash market a few years back - more or less why he's CEO today - you'll understand why flash manufacturers allow Apple to dictate stuff like this.

Other than that, I'm not sure you're going to find much more than that thats "authoritative" I'm afraid. Like you said, most of this stuff is closed source, though you can find traces littered everywhere, with includes like this one. Also, note that TRIM is more of a concept/implementation thing than a standard (at least with anything prior to SATA 3.1).

I can also confidently tell you that TRIM enabled/Apple-logo branded SSDs can only be purchased through GSX (or the grey market). And that Trim Enabler works quite well. I've installed (the more recent versions) in many a production environment.

A couple of links:
http://www.anandtech.com/show/5453/trim-enabler-20-for-os-x-lion-released http://en.wikipedia.org/wiki/Trim_(computing)

Best Answer

Related Solutions

MacOS – How does TRIM Enabler work

MacOS – Does OS X sometimes run a lesser-known TRIM routine with drives that are not explicitly supported

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