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Aftermarket SSD On A MacBook Pro: TRIM Gets Tested

Enabling TRIM Is Almost Always Worth It

We've spent a lot of time talking to storage professionals, including some from LSI, who agree that TRIM is beneficial, even when your controller is designed to make the most of free space on an SSD. So, if a SandForce-based drive can see some benefit, so will any other solid-state repository you install. Consequently, it's worth it to get TRIM working, even when Apple tries to keep you from the command artificially.

To what end does TRIM matter? Well, our AJA System Test and DiskTester benchmarks show that the explicit performance gains, even in a synthetic, are pretty small. In the real world, you probably wouldn't notice one way or the other. But sure, turn TRIM on and things speed up a little bit. 

Source: LSI/SandForce

More important are the endurance-oriented reasons to keep TRIM turned on. Without the command, your operating system knows when data is deleted, but has no way to tell the SSD's controller. In turn, the SSD keeps moving that information around via garbage collection, unnecessarily programming and erasing the flash memory cells with stale data. This means that, at some point, the SSD will fill up with data, leaving the controller only with over-provisioned flash with which to work. That's seven to 12% of most desktop SSDs, and includes the space for firmware features like bad block replacement.