Greetings, With acid-state-0.6, you can use regular Haskell data structures without worrying about data loss or durability. Your state will simply always be available to you even after software crashes or power outages. Important: acid-state-0.6 is not immediately backwards compatible with previous versions. To restore states from previous versions you first need to create a checkpoint and then modify your data structure to use the 'Prim' wrapper from safecopy-0.6 wherever built-in types are used. More information on this will be on the wiki soonish. I hope this slight inconvenience will be worth it in the long run. Acid-state-0.6 also includes a new Remote backend that enables concurrent access by multiple processes. For examples of how to use the library, see: http://mirror.seize.it/acid-state/examples/ Hackage page: http://hackage.haskell.org/package/acid-state Wiki site: http://acid-state.seize.it/ -- Cheers, Lemmih