Shuvendu Lahiri Soft Updates: A solution to metadata update problem in file systems The 3 most interesting points of the paper are : (a) The paper provides an efficient software-solution to the metadata update problem by enforcing fine-grained dependencies for the metadata entries in the write-back caches. The use of fine-grained dependencies eliminate many cyclic(false) dependencies at the block level. (b) The authors carefully analyze the implementation complexities introduced by ``fsync'', unmount, useless write-backs and the ``fsck'' utilities and suggest solutions to overcome them while incorporating soft updates in unix BSD. (c) By maintaining update dependencies, it is sufficient to guarantee the consistency of the on-disk copies of inodes, directories etc., which translates to almost immediate crash-recovery for the file-systems. One of the key problems with this approach is that the deallocated resources do not become available for reuse until the reinitialised inode or indirect block reaches stable storage. The paper provides a very important insight into practical system building. It lists the constraints expected from the ``ideal'' solution for metadata update and then prudently choose to relax immediate stability for improved performance, because it does not aggravate the current stability situation. The careful weighing of different constraints to obtain a feasible solution is a very important characteristic of system design.