On Wed, Oct 14, 2015 at 10:47 PM, Zygo Blaxell <ce3g8jdj@xxxxxxxxxxxxxxxxxxxxx> wrote: > > I wouldn't describe dedup+defrag as unsafe. More like insane. You won't > lose any data, but running both will waste a lot of time and power. > Either one is OK without the other, or applied to non-overlapping sets > of files, but they are operations with opposite results. That is probably why I disabled it then. I now recall past discussion that defragging a file wasn't snapshot-aware, though I thought that was fixed. Obviously there is always a tradeoff since from a dedup perspective you're best off arranging extents so that you're sharing as much as possible, and from a defrag standpoint you want to just have each file have a single extent even if two files differ by a single byte. I've pretty much stopped running VMs on btrfs and I've adjusted my journal settings to something more sane so the defrag isn't nearly as important these days. -- Rich -- 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
