An object-based storage may employ a transactional interface and a copy on write protocol. The inode for the file (which is identified by the I-number and indicates one or more blocks storing the file data) may be copied to a working copy of the inode, and the working copy may be updated to indicate the newly allocated blocks. In response to a file commit (e.g. a file close or a file synchronization command), the working copy of the inode may be atomically written to a non-volatile storage. In this manner, the updates performed during the transaction may be atomically committed to the file. The inode itself may be stored in a file (referred to as the inode file), and the storage may perform updates to the inode file atomically as well. The inode file may be modified using the copy on write protocol described above, and the master inode (mapping the blocks of the inode file) may be atomically written to non-volatile storage to atomically update the inode file. In one particular embodiment, the storage employs a journal technique for updates to the inode file.