If you feel your snazzy new Nexus 6 just isn't performing as quickly and smoothly as it should be, Android 5.0's default full-disk encryption could be to blame. AnandTech recently ran storage performance benchmark tests on two Nexus 6 devices: one with and one without full-disk encryption (FDE) enabled.
The Nexus 6 comes with FDE enabled by default, which you can't turn disable, but the site was able to grab a non-encrypted phone from Motorola.
The results of the tests were staggering. With encryption enabled on the device, the site's benchmark tests saw a 62.9 percent drop in random read performance, a 50.5 percent drop in random write, and 80.7 percent in sequential read.
Long story short: there appears to be an issue with performance lag due to Android Lollipop's FDE. And with the Nexus 6 you pay that performance hit whether you've got your lock screen enabled or not.
Why this matters: Beefed up device encryption is a big deal with the latest generation of smartphones in the wake of Edward Snowden's revelations and rampant security breaches throughout 2014. Apple closed the door on its final back door with the iPhone 6 and iOS 8. Google, which has offered FDE since Android 3.0 Honeycomb, turned it on by default beginning with Android 5.0 (Lollipop) and the Nexus 6.
The idea is to improve privacy by making it harder for general snoops (and law enforcement) to peer into your device without permission. But if FDE means poor device performance, not many people will be willing to pay the price required for extra privacy.
The problem with FDE on Android
The issue, says AnandTech, is that many components commonly used in Android devices just aren't up to the task of incorporating FDE without a performance hit. That will probably change over time, but for now it appears to be a big issue.
For Android encryption to be useful, you also must have the lock screen enabled. Without it, FDE is enabled but it doesn't kick in—yet the cost penalty remains. In other words, you could be experiencing lag on your device even if you're not effectively using FDE.
Older phones that receive Lollipop as an over the air update or flash it to their devices do not get FDE turned on automatically.
Does this mean you shouldn't pick-up the Nexus 6? Probably not. As we said in our review, the 2.7GHz SoC and 3GB RAM makes for snappy performance, including with games. Other sites have also given the Nexus 6 top marks, although The Verge and Droid-Life did notice moments of strange lag.
If you're concerned about the possibility of down-graded performance the best remedy is to try out a Nexus 6 yourself before you buy.