Yes - you would need at least 3 replicas per data center to use LOCAL_QUORUM and survive a node failure.
On Fri, Sep 2, 2011 at 3:51 PM, Oleg Tsvinev <oleg.tsvi...@gmail.com> wrote: > Do you mean I need to configure 3 replicas in each DC and keep using > LOCAL_QUORUM? In which case, if I'm following your logic, even one of > the 3 goes down I'll still have 2 to ensure LOCAL_QUORUM succeeds? > > On Fri, Sep 2, 2011 at 1:44 PM, Nate McCall <n...@datastax.com> wrote: >> In your options, you have configured 2 replicas for each data center: >> Options: [DC2:2, DC1:2] >> >> If one of those replicas is down, then LOCAL_QUORUM will fail as there >> is only one replica left 'locally.' >> >> >> On Fri, Sep 2, 2011 at 3:35 PM, Oleg Tsvinev <oleg.tsvi...@gmail.com> wrote: >>> from http://www.datastax.com/docs/0.8/consistency/index: >>> >>> <A “quorum” of replicas is essentially a majority of replicas, or RF / >>> 2 + 1 with any resulting fractions rounded down.> >>> >>> I have RF=2, so majority of replicas is 2/2+1=2 which I have after 3rd >>> node goes down? >>> >>> On Fri, Sep 2, 2011 at 1:22 PM, Nate McCall <n...@datastax.com> wrote: >>>> It looks like you only have 2 replicas configured in each data center? >>>> >>>> If so, LOCAL_QUORUM cannot be achieved with a host down same as with >>>> QUORUM on RF=2 in a single DC cluster. >>>> >>>> On Fri, Sep 2, 2011 at 1:40 PM, Oleg Tsvinev <oleg.tsvi...@gmail.com> >>>> wrote: >>>>> I believe I don't quite understand semantics of this exception: >>>>> >>>>> me.prettyprint.hector.api.exceptions.HUnavailableException: : May not >>>>> be enough replicas present to handle consistency level. >>>>> >>>>> Does it mean there *might be* enough? >>>>> Does it mean there *is not* enough? >>>>> >>>>> My case is as following - I have 3 nodes with keyspaces configured as >>>>> following: >>>>> >>>>> Replication Strategy: org.apache.cassandra.locator.NetworkTopologyStrategy >>>>> Durable Writes: true >>>>> Options: [DC2:2, DC1:2] >>>>> >>>>> Hector can only connect to nodes in DC1 and configured to neither see >>>>> nor connect to nodes in DC2. This is for replication by Cassandra >>>>> means, asynchronously between datacenters DC1 and DC2. Each of 6 total >>>>> nodes can see any of the remaining 5. >>>>> >>>>> and inserts with LOCAL_QUORUM CL work fine when all 3 nodes are up. >>>>> However, this morning one node went down and I started seeing the >>>>> HUnavailableException: : May not be enough replicas present to handle >>>>> consistency level. >>>>> >>>>> I believed if I have 3 nodes and one goes down, two remaining nodes >>>>> are sufficient for my configuration. >>>>> >>>>> Please help me to understand what's going on. >>>>> >>>> >>> >> >
