For those who are succeeding where others have failed at getting their hands on the public beta of Yosemite, make sure you disable TRIM before installing on a 3rd party solid state drives (SSDs). Users are reporting that having TRIM controls enabled will resort in your Mac not booting up.
A post over at Reddit reports the latest Yosemite beta (Public Beta 1, aka Developer Beta 4) is not loading modified kernel extensions (kext files). Since TRIM support involves modifying a kext file or two, if you leave it enabled, those kexts won't load, and now you're up to your knees in boot failure. That same post also outlines how to disable TRIM for the install and initial boot processes.
TRIM is a set of commands commonly used to communicate with the OS on a lower level, allowing the OS to better communicate free space and improve "garbage collection" on an SSD. Basically, over time, SSD performance will degrade without some sort of garbage collection, so TRIM keeps things nice and perky.
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