For that matter, RF=1 and QUORUM are incompatible (if you want to be able to take a node down).
In other words, if you use QUORUM, you need RF>=3. On Sun, Nov 28, 2010 at 8:04 PM, Jake Luciani <jak...@gmail.com> wrote: > 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 >>>>>> >>>>>> >>>>> >>>> >>> >> >
