Jay R. Ashworth wrote:
> But you see, if the sales pitch is "journalling is worth the speed hit
> because it protects your *data*", then they're lying. It only protects
> your file system structures.
It *can* protect your data, when used in connection with application
programs which do so.
For example, some application programs are written to rely on the
rename() system call being atomic. They'll write out a new, consistent
version of a file, and then rename the new version over the new version.
As long as the file system remains consistent, then the application
data will also be consistent as long as the file system guarantees
consistency.
Other applications may make careful use of O_SYNC or fsync to ensure
consistent data, again assuming that the file system itself remains
consistent.
A journalling file system takes you part of the way to having consistent
data; the applications you use can take you the other part.
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