OpenExtensions for z/VM "Q"s and "A"s

Question: If power drops, are there any exposures in the byte file system (BFS) like the old problems that Unix filesystems used to have (corrupt inodes and so forth, leading to the need to run fsck)? I am not aware of an fsck command in OpenExtensions. Am I correct in assuming that corruption of the vnodes could not take place in these circumstances ?

Answer: You are correct. There is no fsck command and the BFS was designed so that it is not needed. You can lose recent data that is still buffered, but the file system structures, directories, inodes and such, will not be damaged. There is a shadow writing technique that is used to ensure structural changes are always committed atomically. The BFS does its own repair, as needed, on each mount of a file system. This is based on records it keeps of changes in progress.

That said, of course there is always a possibility that user data, critical file system data, or the media can be damaged and prudent backup procedures are always warranted. This is true even if you have an fsck utility, which generally ensures structural integrity, not data integrity.

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