Re: [PATCH 0/2] Check node nums for cluster raid

[Jes Sorensen <Jes.Sorensen@redhat.com>]

Guoqing Jiang <gqjiang@suse.com> writes:
> Hi Jes,
>
> On 05/04/2016 11:12 AM, Jes Sorensen wrote:
>> Guoqing Jiang <gqjiang@suse.com> 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