With Android 5.0 Lollipop, Google has flipped Full Disk Encryption (FDE) to on for all new devices, and the Nexus 6 is among the first devices in the market to ship with FDE enabled.
Now, according to the tests conducted by the folks over at AnandTech, there is a significant NAND performance penalty on the Nexus 6 with the encryption enabled. The performance drop while reading random data was a staggering 62.9%, with the random write data performance dropping by 50.5%. The sequential hit was the worse and reported a drop of nearly 80.7% in performance.
Such a huge hit in NAND performance is easily visible in day-to-day usage, and the Nexus 6 will take longer to open apps, read data and will also stutter under load compared to other smartphones with the feature disabled. Full Disk Encryption is enabled by default on the Nexus 6, and Google does not provide users with a way to disable it.
According to AnandTech’s explanation, all the writes to NANDs are encrypted in Lollipop and are again decrypted before being returned to the process. The passcode lock used by the user is the key used to decrypt the data. This means that if you use your Nexus 6 without any kind of security lock, you will still be hit with the performance drop even though you won’t be able to enjoy the extra layer of security added by FDE.
Apple gets way by enabling disk encryption on its iOS devices because of a low-level dedicated hardware. While the Snapdragon 805 chip inside the Nexus 6 does come with a cryptographic module, Google is not making use of it for reasons unknown to us.