On Wed, Apr 24, 2019 at 05:42:35PM -0400, David Shaw wrote: > My question is why did the --grow manage to increase > the component size in the 3+1 case? Check mdadm --examine for data offset. During a reshape, originally critical data needed to be backed up ( --backup-file ) but at some point mdadm started creating arrays with larger data offset (e.g. 128M depending on device size), and instead of asking for a backup file, it just eats into the offset thus avoiding the critical data issue. With a slightly smaller offset you get a slightly larger space. If you don't like the behavior, it's still possible to create arrays with a simple 1M data offset and depend on --backup-file for reshape operations. Regards Andreas Klauer
