From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jes Sorensen Subject: Re: [PATCH 0/2] Check node nums for cluster raid Date: Thu, 05 May 2016 16:28:55 -0400 Message-ID: References: <1462350824-9872-1-git-send-email-gqjiang@suse.com> <572AB7EF.6090403@suse.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <572AB7EF.6090403@suse.com> (Guoqing Jiang's message of "Wed, 4 May 2016 23:03:11 -0400") Sender: linux-raid-owner@vger.kernel.org To: Guoqing Jiang Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Guoqing Jiang writes: > Hi Jes, > > On 05/04/2016 11:12 AM, Jes Sorensen wrote: >> Guoqing Jiang writes: >>> For cluster raid, we do need at least two nodes for it, >>> the two patches add the checks before create and change >>> bitmap. >>> >>> Thanks, >>> Guoqing >>> >>> Guoqing Jiang (2): >>> Create: check the node nums when create clustered raid >>> super1: don't update node nums if it is not more than 1 >>> >>> Create.c | 7 ++++++- >>> super1.c | 5 +++++ >>> 2 files changed, 11 insertions(+), 1 deletion(-) >> Hi Guoqing, >> >> I am a little confused on this one - albeit I haven't looked at it in >> detail. Why should it not be possible to start a cluster with one node? >> In theory you should be able to do that, and then add nodes later? > > The "nodes" means how many nodes could run with the clustered raid. > IOW, if nodes is set to 1, then we can't assemble the clustered raid in > node B after clustered raid is created in node A. > > And we had provided below protection in md-cluster.c, so it doesn't make > sense to create clustered raid with "nodes = 1" since we can't use this raid > across cluster. > > f (nodes < cinfo->slot_number) { > pr_err("md-cluster: Slot allotted(%d) is greater than > available slots(%d).", > cinfo->slot_number, nodes); > ret = -ERANGE; > goto err; > } OK, thanks for the explanation! I'll apply these shortly. Cheers, Jes