On 05/04/2016 11:12 AM, Jes Sorensen wrote:
> Guoqing Jiang <gqjiang@xxxxxxxx> 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?
Not typically. A single node of a cluster is likely the odd man out, so
starting it and allowing changes to the underlying device has a high
potential of creating split brain issues. For that reason, most cluster
setups require some minimum (usually 2) for a quorum before they will
start. Otherwise, given a three node cluster, you could end up with
three separate live filesystems and the need to merge changes between
them to bring the cluster back into sync.
--
Doug Ledford <dledford@xxxxxxxxxx>
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