Joe Peterson wrote:
My thoughts on what you are saying is that it is not generally a good idea to assume any filesystem will lay things out in any specific way, including whether it has one-to-one mapping of files to blocks. In other words, making a copy of a file on the same filesystem for safety reasons (unless you are modifying a file and want a backup of its old state, like emacs' ~ files) is probably not a great habit to get into. The implementation details of how a filesystem makes things safer should be behind-the-scenes (like checksums, multiple-copies-by-default, mirroring, etc.). That way, you can simply rely on the filesystem to manage protection of your data rather than going to the effort of managing multiple copies of files yourself for that reason.
I'm a filesystem guy so I only use ones I know do what I want, I never trust ones I don't know about :) I agree with you about the danger of assuming what a filesystem will or won't do on local copies. I also fear that 99% of normal users have an expectation that making a copy makes a new physical instance (which of course is not safe if the device crashes either). I hate dealing with customers that have lost their data because of the filesystem. Morey Roof wrote:
I was hoping to have it specified as a set of mount options or defaults controlled in the super block so that if you want to use it you can otherwise it doesn't exist.
I don't have veto power in btrfs so my aversion means nothing. As you say, there are a number of good ways to control it. If you pursue this, I might suggest having a dedup limit so they can say "keep at least 2 copies" or "just one". jim -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
