Messages in this thread | | | Date | Sat, 13 Mar 2004 22:03:05 +0100 | From | Pavel Machek <> | Subject | Re: [PATCH for testing] cow behaviour for hard links |
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On So 13-03-04 20:48:27, Jörn Engel wrote: > On Sat, 13 March 2004 14:43:30 +0100, Pavel Machek wrote: > > > > I do not know your current design, but... > > > > In ideal world there would be no COW links. System would > > magically detect that you are doing cp -a, and would link > > at individual block level. > > > > Well, that would be probably too fs-specific. But introducing copyfile() > > syscall, which would just link the inodes if underlying fs > > supported it might be good start. On first > > write into one > > of linked files copy > > would be done... > > Agreed. > > > Only disadvantage I see is that such links would not survive > > tar-backup... > > That's not a problem either. Have a userspace program that checks all > files and hints for identical ones (new syscall, copyfile() cannot do > this without races). Depending on fs size, the necessary data can > grow into the gigabytes, but the code is just 200 lines.
Hmm, I don't quite like "copyfile if not modified" syscall, but even without that it is usefull...
> Or did you mean the problem of tar backups growing *much* larger than > the real filesystem? Yes, tar becomes useless for backups then. :)
Yep, this is what I meant. Pavel
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