On Sat, Jan 19, 2019 at 09:52:11PM +0500, Roman Mamedov wrote: > Read `man mdadm` for --size. What you need is --array-size. mdadm should even be nice enough to provide the exact size required to make the operation. | # mdadm --grow /dev/md42 --raid-devices=4 | mdadm: this change will reduce the size of the array. | use --grow --array-size first to truncate array. | e.g. mdadm --grow /dev/md42 --array-size 5860011008 (This is just an example.) You have to be really, really sure your filesystem does not exceed the new size. I think mdadm actually accepts G units here, so if you did a resizefs 2345G you can use --array-size=2345G as well (and mdadm will still complain if it's not small enough when trying to reduce number of devices afterwards) Why not switch to RAID-5 instead? Regards Andreas Klauer
