Alice and Bob in I/O Land

file systems (e.g. ext3, xfs, reiserfs) perform journaling - to avoid endless fsck times during a reboot after a system crash.
The basic idea: write the transaction into a journal, before doing the file-system updates.
On mount after a crash - replay the unfinished transactions from the journal.
Note: Linux has "jfs" support in the kernel - to support journals.

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