On 13 Dec 2019, Coly Li spake thusly: > diff --git a/mdadm.8.in b/mdadm.8.in > index 9aec9f4..e5074c0 100644 > --- a/mdadm.8.in > +++ b/mdadm.8.in > @@ -2727,6 +2727,14 @@ option and it is transparent for assembly feature. > .IP \(bu 4 > Roaming between Windows(R) and Linux systems for IMSM metadata is not > supported during grow process. > +.IP \(bu 4 > +When growing a raid0 device, the new component disk size (or external > +backup size) should be larger than LCM(old, new) * chunk-size * 2. Here > +LCM stands for Least Common Multiple calculation, old and new are > +devices' numbers before and after the grow operation, "* 2" comes from > +the fact that mdadm refuses to use more than half of a spare device for > +backup space. Hm, perhaps a slight variation, if I get this right: When growing a raid0 device, the new component disk size (or external backup size) should be larger than LCM(old, new) * chunk-size * 2, where the LCM() is the least common multiple of the old and new count of component disks, and '* 2' comes from the fact that mdadm refuses to use more than half of a spare device for backup space. maybe? (I'm not sure what you mean by "devices' numbers" here.)
