libfiu is a C library for fault injection. It provides functions to mark "points of failure" inside your code (the "core API"), and functions to enable/disable the failure of those points (the "control API"). The core API is used inside the code on which you want to perform failure injection. The control API is used inside the testing code in order to control the injection of failures.
libjio is a C library to do journaled, transaction-oriented I/O. It provides a UNIX-like set of file operation functions (such as open, read, and write), which are wrapped in a transaction framework, so that file operations can be committed or rolled back as necessary. It is non-intrusive, atomic, and thread-safe, with fast crash recovery.
nmdb is a network database (dbm-style) that can use multiple protocols to communicate with its clients. TIPC, TCP, UDP, and SCTP are currently supported. It consists of an in-memory cache that saves (key, value) pairs, and a persistent backend that stores the pairs on disk. Both work in combination, but the use of the backend is optional, so you can use the server only for cache queries, pretty much like memcached.