>>>>> "Bill" == Bill Davidsen <davidsen@xxxxxxx> writes: >> FWIW, XFS and btrfs both use the page writeback bit correctly and >> never change a page while it is undergoing I/O. >> >> Bill> That's necessary but not sufficient. To be done correctly it must Bill> be protected by md as well. This is because arrays are used Bill> without a filesystem by some applications, such as swap and Bill> database, to name the most common cases. I agree that making MD RAID1 do a copy would be a quick fix. But I don't see any reason to encourage what is essentially sloppy behavior at the top of the stack. And then what if you stack MD/DM devices? Do each layer do a copy? I think that gets murky pretty quickly. I'd much rather fix the cases where the top layers are broken. And as I said there are several people working on this spurred by my work on the data integrity extensions. FWIW, databases on raw disk have gone out of fashion. But it is true that applications that do direct I/O need to avoid updating buffers in flight. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
