Google makes full-disk encryption optional for Android devices

Earlier Google had announced that devices shipping with Lollipop pre-installed would have encryption as "out of the box" option.Nexus 6 smartphone and Nexus 9 tablet are shipping with encryption activated. However recently announced Lollipop devices such as Mot E and Samsung Galaxy S6 aren't being fully encrypted automatically. There have been performance concerns regarding enabling full-disk encryption as noted in reviews of  Nexus 5 devices.