CLFS defines a device driver interface (DDI), via which physical storage system specific drivers plug in to the CLFS API. The CLFS driver implements the ARIES recovery algorithm; other algorithms can be supported by using custom drivers.
CLFS supports both dedicated logs, as well as multiplexed logs. A dedicated log contains a single stream of log records whereas multiplexed log contain multiple streams, each stream for a different application. Even though a multiplexed log has multiple streams, logs are flushed to the streams sequentially, in a single batch. CLFS can allocate space for a set of log records ahead-of-time (before the logs are actually generated) to make sure the operation does not fail due to lack of storage space.
A log record in a CLFS stream is first placed to Log I/O Block in a buffer in system memory. Periodically blocks are flushed to stable storage devices. On the storage device, a log contains a set of Containers, which are allocated contiguously, each containing multiple Log I/O Blocks. New log records are appended to the present set. Each record is identified by a Log Sequence Number (LSN), an increasing 32-bit sequence number. The LSN and other metadata are stored in the record header. The LSN encodes the identifier of the container, the offset to the record and the identifier of the record - this information is used to access the log record subsequently. However, the container identifiers are logical identifiers, they must be mapped to physical containers. The mapping is done by CLFS itself.
Patent Issued for System, Method, and Computer Readable Media for Identifying a User-Initiated Log File Record in a Log File
Jul 26, 2012; By a News Reporter-Staff News Editor at Computer Weekly News -- A patent by the inventors Chen, Danny Yen-Fu (Austin, TX); Cox,...
Agency Reviews Patent Application Approval Request for "System, Method, and Computer Readable Media for Identifying a User-Initiated Log File Record in a Log File"
Sep 06, 2012; By a News Reporter-Staff News Editor at Computer Weekly News -- International Business Machines Corporation has been issued...