This module attemtps to provide a storage driver that is really multiple storage drivers. This could be used for storage error tolerance or caching of data in a faster storage driver.
Here data would be first read from or written to mod_storage_memory, then internal storage, then SQL storage. For reads, the first successful read will be used. For writes, it depends on the
storage_multi_policy option. If set to
"all", then all storage backends must report success for the write to be considered successful. Other options are