For those that already have a Nexus 6, you may have noticed the device falling short of expectations given the beastly spec sheet. It turns out there’s a good reason for that. As AnandTech points out, Google’s implementation of device encryption carries a significant performance penalty. According to them, they’re of the opinion that the warm and fuzzy feeling of your personal data being encrypted and protected from prying eyes isn’t worth the hit in disk read/write speeds that results.
You might have noticed Google makes this difficult by not allowing users to disable this encryption from within the OS. If you really want to boost your performance at the expense of device encryption, you can now do so thanks to yet another clever developer over at XDA. There’s no need to have your device rooted yet or have a custom recovery installed — you can do it all in fastboot mode (after unlocking your bootloader, of course).
In his thread, XDA recognized developer bbedward posted the necessary file to flash via fastboot, giving the following instructions:
1.) Reboot to boot loader
2.) Unlock device if not already (fastboot oem unlock) – will wipe all data
3.) I think unlocking the device will automatically run encryption jobs, so don’t boot android write your most important stuff down and then continue without backing it up.
4.) Download the boot.img noencrypt above
5.) Flash it in the bootloader (fastboot flash boot boot_noforceencrypt.img)
6.) If still encrypted, run a factory reset
7.) If it doesn’t work, you can go back into the bootloader and flash the stock image.
8.) Run CF-Auto-Root for root, if desired. Flash TWRP, do wutever you want.
9.) Updates will overwrite this and turn encryption back on, you should probably update manually (or remove the boot.img from the update) if you don’t want encryption to get turned back on (turning it back on may be a PITA in the sense that you’ll have to factory reset to get it off again)
As with any sort of fastboot and/or root tinkering, what you do is at your own risk, and I should point out that the developer who posted the solution doesn’t have a Nexus 6 of his own to actually test with. That being said, neither the developer, XDA, nor Phandroid can be held responsible for any damages to your device. You’ve been warned (and good luck!).