Method of managing data in storage device based on variable size mapping, method of operating storage device using the same and storage device performing the same

A method of managing data in a storage device is provided. The storage device includes a plurality of nonvolatile memory chips each including a plurality of pages. A first data object is received from an external host device. The first data object has an unfixed size and corresponds to a first logical address which is a single address. Based on determining that it is impossible to store the first data in a single page among the plurality of pages, a buffering policy for the first data object is set based on at least one selection parameter. While mapping the first logical address of the first data object and a first physical address of pages in which the first data object is stored, a first buffering direction representing the buffering policy for the first data object is stored with a mapping result.