How to Disable Data Encryption on Nexus 6
In late September, Google decided to step on NSA’s toes and turn on encryption by default in Android Lollipop. The Nexus 6 is the first Google Nexus device to ship with data encryption enabled right out of the box. According to AnandTech, the Google Nexus 6 performance decreases significantly because of encryption.
Data encryption is a software layer. This is a well known fact, since encryption has been available to enable for some time. XDA Recognized Developer bbedward noticed that the encryption is enabled with just one flag available in the device’s fstab. Flashing a boot image with modified fstab should disable the data encryption by default. Bbedward prepared such an image, which can be easily flashed onto your Nexus 6. After switching off the data encryption, your device should start to fly like it should have from the very beginning.
To flash the image, your device must have an unlocked bootloader. Unlocking will erase all your data, so be sure to have a backup handy. If you already have a backup, you need to perform a factory reset to wipe all your data.
The modified boot image with data encryption turned off can be downloaded from the Disable Forced Encryption forum thread. If you own a Google Nexus 6 and would rather have faster storage access speed instead of the greater security you gain from data encryption, head over there to get started.
[Big thanks to XDA Senior Moderator crachel for the tip!]