On Mon, 20 Oct 2014 14:33:31 +0200 Hans Kraus <hans@xxxxxxxxxxxxxx> wrote: > Hi, > > I want to expand an existing root array with an SSD. For that purpose I > try to set firstly 'write-behind' on that array. Afterwards I will add > the SSD, remove the HDs and re-add them with 'write-mostly'. On that > array is the root filesystem, therefore stopping is no option. In > >/home/kraush/work/mdadm/mdadm< is the latest mdadm version from git. > I tried: > ----------------------------------------------------------------------- > root@elefant:/home/kraush/work/mdadm/mdadm# ./mdadm --manage > --write-behind=4096 /dev/md4 > mdadm: :option --write-behind not valid in manage mode > root@elefant:/home/kraush/work/mdadm/mdadm# ./mdadm --grow > --write-behind=4096 /dev/md4 > mdadm: no changes to --grow > ----------------------------------------------------------------------- > What is the correct syntax? > Not quite. "write-behind" is a property of the bitmap. To enable write-behind on an array you first need to remove the bitmap if there is one mdadm /dev/md4 --grow --bitmap=none then add a new bitmap with the required property mdadm /dev/md4 --grow --bitmap=internal --write-behind=4096 NeilBrown
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