TRIM support is coming in OS 10.7 Lion, but that's still a way off, and even then, it'll only work with Apple SSDs.If you have a non-Apple SSD, or you just want to get TRIM support now, previously. How to Enable TRIM on a Mac With SSD The best way to expand your Mac’s lifespan and obtain a significant speed boost is by replacing the hard drive with a solid state drive (SSD). You’ll notice the huge performance improvement right from the first time you boot up and immediately praise yourself for making this investment.

You can also install Cindori's Trim Enabler, available <a href='http://www.groths.org/?p=617'>here</a>.
You'll recognize his name if you've used his utility for flashing non-Apple video card upgrades for Mac Pro towers. Anyway, it simply enables the (obviously) already built-in trim support for almost all SSDs, not just those that are Apple-provided.

You can do the same thing by booting to single user mode (reboot while holding command-s) and entering 'fsck -fy' (without the quotes). If you have the TRIM hack installed, this will TRIM free space on the drive. If the TRIM hack is not installed this will not work.

Of course a ssd from, say OWC, has no need for this. Most of the new SSDs have functions to do garbage collection built into the controller on the drive.
Go look it up on OWCs site.

Built-in garbage collection is guessing at what needs to be reclaimed. TRIM lets the OS tell the SSD directly 'yes, you can free this now'.
No amount of clever GC algorithms can compare to a simple instruction that says 'do this'.

I bought a Vertex2 SSD drive over 7 months ago. I don't use TRIM.
I ran a speed test on the drive right after the purchase.
I ran the same test on the drive just recently. The results were the same.
No loss of speed. The built-in SandForce controller does a good job iIMHO.

Mac Os Ssd Trim

After reading things on the OWC site and on ancillary blogs maintained by their top personnel, I have lost respect for them. One has to be able to differentiate between technical competence and cleverness in self-promotion. I for one am not going to pay someone premium prices for their ability to BS.

I have no second SSD to test. Really curious whether third-party add-on does this, or OS X itself.

External Ssd Trim

My guess is it's a result of the 3rd party TRIM enabler - just did Disk Utility --> Repair on my machine (MacBook 2008 w/ Lion + Crucial SSD) and it didn't say it did a TRIM.

Yeah, don't trim OWC SSDs. Decreases performance. http://blog.macsales.com/11051-to-trim-or-not-to-trim-owc-has-the-answer

Isn't it supposed to happen on the fly ?

Why do you have 'Trim Enabler tool/hack installed'?
Lion supports TRIM.
See: System Information->Serial ATA:
TRIM Support: Yes

Lion only enables TRIM for apple-shipping SSDs. Third-party drives will not get it without a hack.

'Cus I'm running 10.6.8. I'm an old fart set in his ways.

This 'trim' ability is built into Lion's Disk Utility and 'fsck', and works on supported (Apple) SSD drives.
Trim Enabler is not needed.

I installed an SSD into my MacBook Pro over 6 months ago. It is a Vertex2 (with SandForce). I ran some tests on the SSD right after installing it.
Then I ran the same exact test just recently, over six months after the purchase. The performance still the same.
And this is without TRIM.
I think these new SSD drives are doing a great job with doing 'housecleaning' on their own.

Yes, newer drives don’t need this. OWC SSDs are the best there is imho. I’m using their 480 GB 3G model. I’m somewhat glad that my older MBP only does SATA2, otherwise I might not have been able to hold myself back ordering the 6G… :-)