By default, the file system is configured as two logical disk partitions: system (root or firmware) partition and user data partition.
The system partition contains the OS and all of the preloaded applications used with the iPhone. The system partition is mounted as read-only unless an OS upgrade is in progress or the device is jailbroken. The partition is updated only when a firmware upgrade is performed on the device. During this process, the entire partition is formatted by iTunes without affecting any of the user data. The system partition takes only a small portion of storage space, normally between 0.9 GB and 2.7 GB, depending on the size of the NAND drive. As the system partition was designed to remain in factory state for the entire life of the iPhone, there is typically little useful evidentiary information that can be obtained from it. If the iOS device is jailbroken, files containing information regarding the jailbreak and user data may be resident on the system partition...