On Wed, Mar 19, 2014 at 10:53:33AM -0600, Chris Murphy wrote: > > On Mar 19, 2014, at 9:40 AM, Marc MERLIN <m...@merlins.org> wrote: > > > > After adding a drive, I couldn't quite tell if it was striping over 11 > > drive2 or 10, but it felt that at least at times, it was striping over 11 > > drives with write failures on the missing drive. > > I can't prove it, but I'm thinking the new data I was writing was being > > striped in degraded mode. > > Well it does sound fragile after all to add a drive to a degraded array, > especially when it's not expressly treating the faulty drive as faulty. I > think iotop will show what block devices are being written to. And in a VM > it's easy (albeit rudimentary) with sparse files, as you can see them grow. > > > > > Yes, although it's limited, you apparently only lose new data that was added > > after you went into degraded mode and only if you add another drive where > > you write more data. > > In real life this shouldn't be too common, even if it is indeed a bug. > > It's entirely plausible a drive power/data cable becomes lose, runs for hours > degraded before the wayward device is reseated. It'll be common enough. It's > definitely not OK for all of that data in the interim to vanish just because > the volume has resumed from degraded to normal. Two states of data, normal vs > degraded, is scary. It sounds like totally silent data loss. So yeah if it's > reproducible it's worthy of a separate bug.
I just got around to filing that bug: https://bugzilla.kernel.org/show_bug.cgi?id=72811 In other news, I was able to 1) remove a drive 2) mount degraded 3) add a new drive 4) rebalance (that took 2 days with little data, 4 deadlocks and reboots though) 5) remove the missing drive from the filesystem 6) remount the array without -o degraded Now, I'm testing 1) add a new drive 2 remove a working drive 3) automatic rebalance from #2 should rebuild on the new drive automatically Marc -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/ -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
