Messages in this thread | | | Date | Sat, 13 Mar 2004 20:48:27 +0100 | From | Jörn Engel <> | Subject | Re: [PATCH for testing] cow behaviour for hard links |
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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.
Or did you mean the problem of tar backups growing *much* larger than the real filesystem? Yes, tar becomes useless for backups then. :)
Jörn
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