Apple released iOS 8.1.1 and suggested that this is not only the normal bug fix and security update but it will also speed up the two devices of Apple which is currently owned by many people. These two devices are Apple iPhone 4s and Apple iPad Air 2. Being old hardware, speed of both devices is disturbed by the latest iOS 8 update, but the latest build will help them to speed up again.
IOS 8.1.1 update is fixing the bugs of iCloud Drive and iWork. This update requires only 65MB, so it won’t be taking long to download it. Apple Smartphones including iPhone 4S, iPhone 5, iPhone 5S, iPhone 5C, iPhone 6 and iPhone 6 will be getting this update. All iPads which recently received iOS 8 will be getting this update as well.
Although update is lightweight but you should try to update it through WI-FI in order to avoid disturbance. You can check update by simple going to setting menu > General and Software update. Before downloading update your device should have at least 50% battery, so that device might not turn off during the update process.