Right. On Sun, Nov 28, 2010 at 1:03 PM, David Boxenhorn <da...@lookin2.com> wrote:
> OK. To sum up: RF=2 and QUORUM are incompatible (if you want to be able to > take a node down). > > Right? > > On Sun, Nov 28, 2010 at 7:59 PM, Jake Luciani <jak...@gmail.com> wrote: > >> I was wrong on this scenario and I'll explain where I was incorrect. >> >> Hints are stored for a downed node but they don't count towards meeting a >> consistency level. >> Let's take 2 scenarios: >> >> RF=6, Nodes=10 >> >> If you READ/WRITE with CL.QUORUM you will need 4 alive nodes if one is >> down it will still have 4 active replicas to write to, one of these will >> store a hint and update the downed node when it comes back. >> >> RF=2, Nodes=3 >> >> If you READ/WRITE with CL.QUORUM you need 2 live nodes. If one of these 2 >> are down you can't meet the QUORUM level so the write will fail. >> >> In your scenario your best bet is to update to RF=3, then any two nodes >> will accept QUORUM >> >> Sorry for the confusion, >> >> -Jake >> >> On Sun, Nov 28, 2010 at 12:26 PM, David Boxenhorn <da...@lookin2.com>wrote: >> >>> Thank you, Jake. It does... except that in another context you told me: >>> >>> Hints only happen when a node is unavailable and you are writing with >>> CL.ANY >>> If you never write with CL.ANY then you can turn off hinted handoff. >>> >>> How do I reconcile this? >>> >>> >>> On Sun, Nov 28, 2010 at 7:11 PM, Jake Luciani <jak...@gmail.com> wrote: >>> >>>> If you read/write data with quorum then you can safely take a node down >>>> in this scenario. Subsequent writes will use hinted handoff to be passed >>>> to >>>> the node when it comes back up. >>>> >>>> More info is here: http://wiki.apache.org/cassandra/HintedHandoff >>>> >>>> Does that answer your question? >>>> >>>> -Jake >>>> >>>> >>>> On Sun, Nov 28, 2010 at 9:42 AM, Ran Tavory <ran...@gmail.com> wrote: >>>> >>>>> to me it makes sense that if hinted handoff is off then cassandra >>>>> cannot satisfy 2 out of every 3rd writes writes when one of the nodes is >>>>> down since this node is the designated node of 2/3 writes. >>>>> But I don't remember reading this somewhere. Does hinted handoff affect >>>>> David's situation? >>>>> (David, did you disable HH in your storage-config? >>>>> <HintedHandoffEnabled>false</HintedHandoffEnabled>) >>>>> >>>>> >>>>> On Sun, Nov 28, 2010 at 4:32 PM, David Boxenhorn <da...@lookin2.com>wrote: >>>>> >>>>>> For the vast majority of my data usage eventual consistency is fine >>>>>> (i.e. CL=ONE) but I have a small amount of critical data for which I read >>>>>> and write using CL=QUORUM. >>>>>> >>>>>> If I have a cluster with 3 nodes and RF=2, and CL=QUORUM does that >>>>>> mean that a value can be read from or written to any 2 nodes, or does it >>>>>> have to be the particular 2 nodes that store the data? If it is the >>>>>> particular 2 nodes that store the data, that means that I can't even take >>>>>> down one node, since it will be the mandatory 2nd node for 1/3 of my >>>>>> data... >>>>>> >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> /Ran >>>>> >>>>> >>>> >>> >> >
