Why OS X doesn't support Trim yet in 2011

What is most disconcerting about the mad rush to install SSDs is that people do no research before-hand.
Apple locked TRIM support for a very good reason — their code works reliably with the SSD’s they’ve chosen to use and no others, because they have programmed in nanosecond-critical timing loops that match perfectly with the access timings of the controllers used in Apple’s SSDs. Using these drivers with other controllers can, at best, slow them down, and at worst, increase the thermal effect that kills storage cells by forcing the controller to act when it isn’t quite ready. This thermal increase hastens the death of the SSD, reducing the already-low lifespan down to six months, if not less.
Then there is the Sandforce issue. SSDs which use one of Sandforce’s DuraClass controllers (SF1200 or better) do not need TRIM at all, as they have their own garbage collection and wear levelling system built in which uses parallel writes, as there are actually two sets of chip controllers built in — whilst one is satisfying the demands of the host in reading & writing requested data, the other is autonomously managing the solid state arrays, shifting regularly-accessed data into new cells, updating block indexes and generally spreading the workload around to ensure thermal effects are kept to an absolute minimum. By enabling TRIM, the SSD is forced to work twice as hard as there are now two separate element management systems running, one from the OS and one built into the device itself. This dramatically increases thermal damage, and again, reducing the life-span of the drive.
Until Apple can implement an intelligent TRIM system — one that can respond to the SSD’s built in characteristics data and adjust its own timings to match, as Windows does — then the only safe, reliable non-factory SSD you can trust with Mac OS X is Intel’s X-25 series. Everything else dies after six to ten months’ regular use.

I work for a major reseller, and we’ve fitted SSDs into machines since they were introduced, and long before Apple began using them themselves — I would estimate the number sold and/or installed would be close to three thousand over the past five years. We’ve had enough come back to determine that solid state storage is an inherently flawed technology, and that Mac OS X is possibly the harshest OS to use with it. Apple’s choice of SSD, coupled with their device-specific coding, means that Apple-shipped SSDs are about as reliable as they can be, but we still see a lot of Airs with SSDs come back within the first twelve months for a module replacement.
The finding that solid-state storage is flawed is echoed by many of my counterparts in the generic-PC business, as well as other Apple technicians I know and others I have conversed with. It has been exceptionally rare to find a solid-state drive in a desktop-OS environment that has remained functional for more than a year, and that six to ten months seems to be the average irrespective of brand … with the exception of Intel’s X-25 series. It is why we now strongly recommend to all customers who use SSDs to maintain a constant, ruthless backup regime.
What causes SSD failure is heat, and every write to solid-state storage is akin to a cigarette to the lungs — it causes minute, cumulative, and irrepairable damage. The principle behind wear-levelling is to distribute all writes evenly across the entire drive, as a single write cycle is actually a multiple-pass operation (read-erase-write-read-write-read) that applies to an entire block. Too many writes within close physical proximity to each other results in a localised rise in temperature above tolerance limitations.
The solid state FLASH array chips used in Intel’s X-25 series have both a much wider gate spacing on the silicon, and a much denser chip packaging material which is a better thermal conductor than the norm. Because of these two factors, localised thermal buildup does not happen to anywhere near the same extent as other brands, resulting in better temperature stability across the surface of the FLASH silicon and thus, a longer operational life-span.

Click to expand...

Lokheed said:

As many of you know, Cindori hacked in TRIM support from the first public release of 10.6.7, which included an updated kernel extension that enabled TRIM for Apple SSDs.

This started a ridiculous trend that saw a maelstrom of SSD owners froth at the mouth and jump at the opportunity (I was one of them, with mixed results). When Lion came out, some tried Cindori's hack with success, others, not so.

Then Grant Pannell came on the scene and further hacked the kext file to support Lion. Again, all SSD owners were satiated.

But before I jumped onto the ship, I started reading Pannell's blog comments (it can be a great way of knowing what you're getting yourself into sometimes) and one user caught my eye: Hyram. They wrote the following:



I haven't experienced the ridiculously short uptime he talks about. I've owned my SSD for almost a year now and it's been humming along nicely. But the "nano-second" timing he talks of made me cautious. The fact that performance went down (by a few marks, but still) and that emptying the trash sometimes took ages also weighed against hacking my kext.

I admit I don't know nearly enough about SSDs and TRIM (not at the level required) to make the call to hack my kernel extension so that DU reads, TRIM: YES.

I guess just a cautionary note to those blindly enabling TRIM (or whining about it) because it was all the rage in 2006. Maybe you want to either learn more about TRIM (is it even needed these days?) or at the very least, be sure enabling it doesn't lead to a detriment...

Click to expand...

BRLawyer said:

I've read the same post by Hyram, and definitely don't feel the need to hack my OS just to "nominally" enable TRIM - Apple's concern is that TRIM needs some timing-customization to work correctly in specific SSDs; and as expected, the company IS NOT in a position to support any SSD out there for this very reason.

Besides, TRIM is NOT necessary for the Vertex 3 due to its SandForce-enabled garbage collection technology. Those using TRIM Enabler do it at their own risk.

Click to expand...

Lokheed said:

Just to add, the Vertex2's also don't need TRIM as they have the same SandForce enabled onboard garbage collection.

As I said, I'm not a super expert on this matter, but the more I read, the more I'm getting that TRIM is a deprecated system...

Click to expand...

MBHockey said:

Unless you have an older non-Sandforce drive, like me.

Click to expand...