On Wed, Apr 10, 2019 at 03:35:46PM +1000, Eyal Lebedinsky wrote: > I have a raid6 with 7 devices which is larger than needed now. Download more things until it's just right. ;-) > One disk needs replacement So replace it before doing anything else. > I will first resize (shrink) the fs, then reduce the array size (--array-size=). mdadm --grow --raid-devices=6 should tell you the correct value for --array-size. Then you know what exactly to shrink the filesystem to, so it's neither too large nor too small. > but I do not know how to nominate which of the 7 devices to remove. Not really possible. Shrinking a RAID6 with a drive missing still has a missing drive. Of course, you can re-sync the leftover drive afterwards. However since you'll be getting a replacement drive anyways, just replace the drive first. Then ... consider not shrinking it at all. Esp. if you have plans to re-grow it later, it's just not worth it. Regards Andreas Klauer
