Doug Ledford <dledford@xxxxxxxxxx> writes: > 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. Valid point, but it still looks like a duplicate of the classic raid1 situation. We still allow the creation of a raid1 with just one drive, would it not make more sense to spit out a warning here, rather than deny it? Cheers, Jes -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
