Disclosed is a 2-level cache system for a Redundant Array of Independent Disks (RAID) device used as part of a Storage Area Network (SAN) system. The RAID controller of the RAID device contains a level 1 cache contained in the RAID controller RAM, and a level 2 cache is created in a Log-structured File System (LFS) portion of a local hard disk drive of the RAID device. The 2-level cache system provides increased data integrity and reliability, as well as less fragmentation of the data frame, for communications with remote storage devices in a SAN system. The increased performance is due to data caching being done at the RAM and disk level instead of data being sent directly to the transmit buffer. The 2-level cache system delays data transmissions until there is system idle time, thus, providing efficient bandwidth utilization of SAN communications, as well as improved resource allocation at the RAID controller level. The 2-level cache system can avoid transmissions across the SAN communication link, thus, freeing RAID controller resources for other purposes when the data frames do not need to be transmitted. The level 2 cache on the log-structured file system disk records a timestamp of each entry in the level 2 cache, making data recovery after a system malfunction faster and easier.

 
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> Methods and apparatus for providing cache state information

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