Abstract: Updating a single block of metadata is optimized into a single I/O operation. Resilience against single block failure and system crashes with a single or less than three I/O operations is provided. The present invention method and apparatus stores two copies of the metadata in two areas on disk. Each individual block of metadata in each area is duplicated as a doublet. The doublet provides two copies of a subject block to be written to disk as a single I/O. This enables metadata to survive a single block failure since such a failure only affects half of the doublet. Further, each block of metadata has header information including an indication of transaction and a part count. A transaction is not deemed committed until corresponding blocks of all parts are found.