A method and apparatus for placing objects on a storage device of a storage system and reconstructing data of objects in the storage device. The storage system stores data as objects and implements a RAID architecture including a plurality of the storage devices, and a disk controller for processing Object-based Storage Device (OSD) commands. Each object includes data and attribute. Parity data is calculated for reconstructing an object upon occurrence of a storage device failure. Each storage device includes plural stripes each having a predetermined length. Each object is stored in a stripe wherein an attribute is stored in the head of the stripe and data is stored after the attribute. When the object size exceeds the stripe length, the remainder of the object is stored in the next stripe, and when another object is to be stored, an attribute is stored at a head of a further next stripe and data is stored just after the attribute.