From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Kraus Subject: How do I set 'write-behind' on existing array? Date: Mon, 20 Oct 2014 14:33:31 +0200 Message-ID: <5445011B.8040008@hanswkraus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids 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? Regards, Hans