Using a third party SSD on your Mac while trying to keep TRIM enabled kind of drives you crazy, and OS X Yosemite didn’t help. Here’s my procedure for keeping my SSD reasonably trimmed while keeping my mind reasonably sane. It may work for you too.
Find an external disk, preferably a 2.5” one. If you’re like me then you have a bunch of spare 2.5” SATA disks on a shelf somewhere - pick a lucky winner and buy a $10 USB enclosure for it.
Install OS X 10.8 (10.9 may also work well) on the external disk. Boot it up (hold
alt upon boot to select it). Disable automatic OS X updates. Keep it offline because it is (or will become) obsolete in terms of security updates.
Enable TRIM via the hack you know of already. It doesn’t really matter how you do it - the “TRIM Enabler” app will work fine. Reboot and verify that System Report says “TRIM Support: Yes”.
Once every 1 to 3 months, you’ll boot your Mac with the USB disk. Open Disk Utility, select your SSD partition(s) - do not select the entire disk - click Repair Disk and wait a minute or two. The log should say “Trimming unused blocks.” You can reboot back into your main system immediately. The whole procedure should just take a couple of minutes.
I found this to strike a nice balance between sanity and perf. Oh and yes, any TRIM-aware SSD will benefit from this treatment - however great its GC may be. Good luck!
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