Think carefully before installing Yosemite on a 3rd party SSD!!

[Chakravartin]

Apple only supports using TRIM on their own SSDs.

Previously, you could patch Apple's TRIM extension so that the OS would use TRIM with any SSD.

Yosemite, introduced code-signed kexts. Modifications to kernel extensions are detected and the OS will FAIL TO BOOT if there's an unsigned kext in the system. TRIM enabler works by modifying an Apple kernel extension, so it doesn't work anymore - unless you apply an additional hack.

The maker of TRIM Enabler has come up with a hack to disable code-signing checks, but it is temporary and will go away if you zap PRAM. This means that just zapping PRAM (or letting the battery run down in your laptop) can cause your Mac to fail to boot.

TRIM extends the life of SSDs. Apple has decided that any SSDs not sold by them (at outrageously high prices) at the point of sale with a Mac should die young.

[richorlin]

Here's the fix for that when using Trim Enabler:

http://www.cindori.org/update-on-trim-in-yosemite/

http://www.cindori.org/trim-enabler-and-yosemite/

I can vouch that it works. I'm typing this on an iMac that boots from an external Samsung SSD drive and Trim shows as enabled in System Report

[sekker]

My iMac boots off an OWC SSD just fine with 10.10.

OWC includes garbage collection in its firmware, as do many other name-brand SSD manufacturers.

Not sure this is a big deal unless you have an older SSD.

[Chakravartin]

sekker wrote:
OWC includes garbage collection in its firmware, as do many other name-brand SSD manufacturers.

Not sure this is a big deal unless you have an older SSD.

Garbage collection is not TRIM.

http://www.tomshardware.com/forum/279412...dead-horse

...4. TRIM is beneficial to all SSDs regardless of what kind of garbage collection is used. I talk about how TRIM came into existence and why it is necessary in my blog http://blog.lsi.com/did-you-know-hdds-do-not-have-a-del... . The TRIM command is sent by the OS to the SSD to identify what pages of data can be ignored during garbage collection. The SSD cannot tell what files have been deleted until the OS uses the same sectors to store new files, but by that time the SSD has already wasted cycles by garbage collecting data that was invalid, but known to the SSD.

5. TRIM will benefit all SSDs in some way. Some will benefit more than others depending upon their situation.

...

9. Garbage collection without TRIM will always be moving all invalid data during the GC process acting like the SSD is operating at full capacity. Only the TRIM command can identify the invalid data and improve performance.

10. A 128GB SSD with TRIM and only 64GB of user data will operate like an SSD with 64GB of over provisioning, meaning it will operate at its fastest level.

11. TRIM identifies what the OS no longer wants to save, but nothing changes on the SSD until the GC process actually recycles that block of pages and skips the TRIMed invalid data.

12. GC is not a replacement for TRIM regardless of foreground or background type. TRIM can only make the GC process more efficient and lower the write amplification...

...the performance gain after TRIM comes from two places. First, TRIM tells the SSD to stop tracking invalid data during garbage collection. This speeds up the garbage collection process. Second, the pages of data that are now freed up will automatically turn into "dynamic" over provisioning. Since larger amounts of over provisioning will improve SSD performance, this increased dynamic over provisioning helps as well.

[sekker]

With an OWC SSD, they claim no need for TRIM:

http://blog.macsales.com/21641-with-an-o...d-for-trim

Crucial also made similar claims when I last checked, will look for the link later.

Ok. Here's one link, not mac-specific

http://forum.crucial.com/t5/Crucial-SSDs...a-p/100276

It see,s to suggest that crucial SSDs can benefit from TRIM.

But I know there was a posting discussing this topic posted by a crucial engineer, and they indicated their firmware was built to keep performance high without active TRIM.

I'd sure like to see some real-world data on this.

[Chakravartin]

sekker wrote:
With an OWC SSD, they claim no need for TRIM

A little disingenuous.

No need for TRIM if all that you care about is okay speed from your SSD (at least it'll be okay until it approaches capacity - that over-provisioning doesn't help much on smaller SSDs and will help less over time as wear-leveling eats into it), but no mention of the abbreviated lifespan from Garbage Collection shuffling around "deleted" bits over and over again.

Note that Larry was talking about the speed benefits of using SandForce controllers and it's a guy from SandForce who made those remarks that I quoted.

[Black]

Interesting-- last time I tried there was no Trim enabler for external SSDs.

[sekker]

OWC has some real-world data showing no significant speed reduction in their SSDs over a 3 year time-period.

But that data is a little old.

I'd like to see some recent data comparing these firmware and TRIM solutions.

[Black]

sekker wrote:
OWC has some real-world data showing no significant speed reduction in their SSDs over a 3 year time-period.

But that data is a little old.

I'd like to see some recent data comparing these firmware and TRIM solutions.

TRIM happens in addition to firmware-based garbage collection-- it's not an either-or. If you don't understand how TRIM complements garbage collection, I'm guessing you may want to bone up on what the terms mean exactly. I'm not seeing why you would not want to have something enabled that can extend the life of your drive.

[Black]

Good primer that specifically addresses how TRIM complements even OWC Larry's magic garbage collection:
http://www.thessdreview.com/daily-news/l...-primer/3/