Dear Coly, Thank you for improving the documentation. On 2019-11-05 08:55, Coly Li wrote: > When growing a raid0 device, if the new component disk size is not > big enough, the grow operation may fail due to lack of backup space. > > The minimum backup space should be larger than > LCM(old, new) * chunk-size * 2 > Here LCM stands for Least Common Multiple calculation, old and new > are devices number before and after the grow operation, "* 2" comes device numbers > from the fact that mdadm refuses to use more than half of a spare > device for backup space. > > There are users reported such failure when they grew a raid0 array There are users reporting … > with small component disk. Neil Brown points out this is not a bug > and how the failure comes. This patch adds note information into > mdadm(8) man page in the Notes part of GROW MODE section, to explain Comma can be removed. > a minimum size requirement of new component disk size or external s/a/the/ > backup size. > > Signed-off-by: Coly Li <colyli@xxxxxxx> > Cc: NeilBrown <neilb@xxxxxxx> > --- > mdadm.8.in | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mdadm.8.in b/mdadm.8.in > index 9aec9f4..dfb55e3 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 number before and after the grow operation, "* 2" comes from device numbers Note, that I am not a native speaker. > +the fact that mdadm refuses to use more than half of a spare device for > +backup space. > + > > .SS SIZE CHANGES > Normally when an array is built the "size" is taken from the smallest Kind regards, Paul
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