In case of a node failure, fsck(8) must be executed for an ordinary file system to recover consistency. In most file systems, it is necessary to inspect all of the meta-data for the systems in order to recover consistency. If a node failure occurs, considerable time may be required before the file system actually becomes available.
The GFS Shared File System records operations that have changed the file system structure in an area called updated log. These operations include file creation and deletion. Using the data in the update log area allows the file system to recover from a system failure in less than a minute.
When recovering from a system failure, the GFS Shared File System retrieves the update log in the recovery process. The file system then decides whether to invalidate or complete the file system operation that was done, and reflects the result. The file system structure can then be mounted and used without fully checking it.
As mentioned in "1.3.1 Uninterrupted operation in case of node failure", the GFS Shared File System operating on multiple nodes does not require execution of sfcfsck(8) because recovery processing of consistency is performed automatically in case of a node failure.
Note
The sfcfsck(8) full check mode is also provided. To recover the file system from a hardware failure on the disk, execution of sfcfsck(8) in the full check mode may be required.
