Bryan Henderson wrote: >> Part of the problem is that "whenever you modify a file" >> is ill-defined, or rather, if you were to take the literal meaning of it >> you'd end up with an unmanageable number of revisions. > > Let me expand on that. Do you want to save a revision every time the user > types in an editor? Every time he runs a "save" command? Every time a > program does a write() system call? Every time a program closes a > modified file? If you're adding to a C program, is every draft you > compile a revision, or just the final modification after the bugs are > worked out? > > When I was very new to coding, I used VMS and thought the automatic > revisioning would be a great thing because it would save me when I > modified a program and later regretted it. The system made a revision > every time I exited the editor. But I soon found that the "previous > revision" to which I wanted to revert was always many editings back, since > I spent a lot of time trying to make the regrettable code work before > giving up. VMS kept a fixed number of revisions per file. But keeping 20 > versions of other files would have been wasteful of disk space, directory > listing space, etc. > > Later, I discovered what I think are superior alternatives: RCS-style > version management on top of the filesystem, and automatic versioning > based on time instead of count of "modifications." For example, make a > copy of every changed file every hour and keep it for a day and keep one > of those for a week, and keep one of those for a month, etc. This works > even without snapshot technology and even without sub-file deltas. But of > course, it's better with those. >From what I can see this seems to be the consesus (and it sound very sensible to me). The question remains is where to implement versioning: directly in individual filesystems or in the vfs code so all filesystems can use it? Jack - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
