And now, when I have one node down with no chance of bringing it back anytime soon, can I still change RF to 3 and get restore functionality of my cluster? Should I run 'nodetool repair' or simple keyspace update will suffice?
On Fri, Sep 2, 2011 at 1:55 PM, Nate McCall <n...@datastax.com> wrote: > 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. >>>>>> >>>>> >>>> >>> >> >
