On Sun, Sep 25, 2016 at 02:25:32AM +0300, Alexander Tomokhov wrote: > Ok, so data checksumming does not remain for newly created empty files > with No_COW attribute. I think it's an important trait of Btrfs behavior > and should be added to wiki. So that users are informed that disabling > CoW on a per-file basis also loses checksum correctness of such file. Actually, it disables pretty much all btrfs features except for... CoW. You lose: * checksums * compression * safety against power loss (torn writes, etc) * transactions (not that anyone uses them...) * etc But, CoW is still there. Try it: make a subvolume, create a FS_NO_COW file (preferably one big enough), snapshot the subvolume, filefrag -v both copies. Write to one of them, changing only a part of file. Wait for writeout, filefrag -v them again. -- An imaginary friend squared is a real enemy. -- 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
