Log-structured file system: Difference between revisions

Revision as of 17:50, 6 September 2011

Revision as of 15:17, 25 October 2011

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Log-structured file systems, however, must reclaim free space from the tail of the log to prevent the file system from becoming full when the head of the log wraps around to meet it. The tail can release space and move forward by skipping over data for which newer versions exist farther ahead in the log. If there are no newer versions, then the data is moved and appended to the head.

To reduce the overhead incurred by this [[garbage collection (computer science)|garbage collection]], most implementations avoid purely circular logs and divide up their storage into segments. The head of the log advances simply advances into non-adjacent segments which are already free. If space is needed, the least-full segments are reclaimed first. This decreases the I/O load of the garbage collector, but becomes increasingly ineffective as the file system fills up and nears capacity.

== Implementations ==