Reducing metadata in a write-anywhere storage system

A computer system comprising:

• a plurality of clients including a plurality of processors;
• a plurality of storage nodes coupled with the plurality of clients;
• a memory management unit included in each of the clients, the memory management unit including a multi-tiered cache memory, the cache memory including an upper level comprising an extent cache and an extent index and a lower level comprising a commit cache and a commit index, wherein each client and corresponding memory management unit operate in conjunction to perform actions including:
• receiving a write request for a data item;
• storing the data item in the extent cache while concurrently storing metadata for the data item in the extent index including updating an interval tree, the updating including
• evaluating the interval tree to determine if the data item overlaps or is adjacent to an already cached data item,
• when the data item overlaps or is adjacent to an already cached data item, merging the metadata for the data item into the interval tree,
• when the data item overlaps or is adjacent to an already cached data item, adding a new metadata entry for the data item into the interval tree;
• upon receipt of a first interrupt or event, moving the data item and the meta data for the data item from the extent cache and the extent index to the commit cache and the commit index;
• upon receipt of a second interrupt or event, moving the data item from the commit cache to a primary storage device and removing the metadata for the data item from the commit index.