そういえば、manコマンドでmdadmの英語の説明をがんばって読んでいたら、微妙に気になる記述を発見。 MDADM(8) MDADM(8) NAME mdadm - manage MD devices aka Linux Software RAID SYNOPSIS mdadm [mode] [options] (途中省略) Grow Grow (or shrink) an array, or otherwise reshape it in some way. Currently supported growth options including changing the active size of component devices and changing the number of active devices in RAID levels 1/4/5/6, as well as