Optimized file creation in WAN-optimized storage

The file creation on remote data storage accessible via a WAN can be optimized by creating temporary files in advance on a remote data storage. The file handles or other file access parameters for these temporary files are cached at a client network location. A file creation request from a client is intercepted at the client network location and one of the cached file handle is returned to the client. This enables the client to immediately write data to the corresponding temporary file, avoiding the delay incurred by communicating the file creation request and its response over a WAN. One or more storage commands are sent to the remote data storage to change the attributes of the temporary file to match those requested by the client, such as the file name, directory, and/or file permissions. File creation requests may be selectively optimized according to rules or criteria specified by users.