Several sites already reported about all the best new features in iOS 10.3, but a few were drawn to one feature in particular, a hidden change that gives the iPhone and iPad a nice little speed boost. For those who has not updated yet, there’s one feature that could pose some serious problems.
Among the behind-the-scenes changes in iOS 10.3, Apple's move to a new file system is clearly the biggest. Prior to iOS 10.3, all iOS devices used the popular HFS+ file system. Beginning with iOS 10.3, however, Apple has moved to the more modern Apple File System (APFS).
There are a number of advantages to switching to Apple’s new file system, but the big ones are better optimization for NAND flash storage and SSD storage, more accurate time stamping, and support for stronger encryption. HFS+ is 30 years old at this point, so it was clearly time for a change.
Here’s the problem, however: once the user updates their phone to iOS 10.3 and their file system is converted to APFS, they can no longer roll back without wiping their phone and reinstalling an older iOS build. Why is that significant? Because if something goes wrong and the user decides to roll back to an older build, they will no longer be able to recover data because everything will have been converted to APFS.
So, a word of warning: Back. Up.
For those who have yet upgraded to iOS 10.3, it is advisable to back up all data before the update. This can be done either with iCloud (Settings > iCloud > iCloud Backup > Back Up Now) or by backing up using iTunes. It might take a little while, but waiting a few minutes while the iPhone backs up is much less aggravating than losing some or even all of the data.