Matthew Garrett: Reducing disk use
UNIX filesystems generally store three pieces of timing information about files – ctime (when the file was changed in any way), mtime (when the file contents, as opposed to its metadata, was last changed) and atime (when the file was last accessed by any process). This is a usefully flexible system, but the semantics of atime can be troublesome. atime must be updated every time a file is read, causing a read operation to instead become a read/write operation. This results in a surprising amount of io being generated in normal filesystem use, slowing the more relevant io and causing disks to spin up due to atime updates being required even if the file was read out of cache. It also results in a lot of unnecessary activity on flash media which may reduce their lifetime.
Man kennt ja die Tips mit noatime und in seinem Blog erklärt Matthew, warum man genau das nicht machen sollte und eine Diskussion in den Kommentare gibt weiteren Aufschluss.