File systems can get corrupted when the i-node or superblock information for the directory structure of the file system gets corrupted. This can be caused by a hardware-related ailment or by a program that gets corrupted that accesses the i-node or superblock information directly. (Programs written in assembler and C can bypass the operating system and write directly to the hardware.) One symptom of a corrupt file system is that the system cannot locate or read/write data located in the particular file system.
A disk drive can intermittently (or permanently) suffer read/write problems. If you hear a drive that makes loud squealing or scratching noises, it probably is about to fail. Usually, however, you will not notice that a drive has gone bad while it is still running. It is when you try to restart the system that the device refuses to work. (At this point, it is usually too late to retrieve the lost data.)
A controller failure can act much like a drive failure. However, when a drive fails, you cannot access that particular drive; when a controller fails, you cannot get access to all of the drives in the system (or many of them). A controller fails because some electrical component on the controller board fails.
Note: Hardware problems are usually the most difficult to diagnose. No two hardware failures are exactly the same. This is usually the case because different components on the same kind of board can fail, causing a totally different set of symptoms and problems. For help in diagnosing hardware problems, refer to the AIX Version 4.3 Problem Solving Guide and Reference.
You must have root user or system group authority to execute this task.