Return-Path: Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: (qmail 99011 invoked from network); 7 Jun 2010 16:05:41 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 7 Jun 2010 16:05:41 -0000 Received: (qmail 84835 invoked by uid 500); 7 Jun 2010 16:05:40 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 84810 invoked by uid 500); 7 Jun 2010 16:05:40 -0000 Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@cassandra.apache.org Delivered-To: mailing list user@cassandra.apache.org Received: (qmail 84802 invoked by uid 99); 7 Jun 2010 16:05:40 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 07 Jun 2010 16:05:40 +0000 X-ASF-Spam-Status: No, hits=2.4 required=10.0 tests=AWL,FS_REPLICA,RCVD_IN_DNSWL_NONE,SPF_NEUTRAL X-Spam-Check-By: apache.org Received-SPF: neutral (athena.apache.org: local policy) Received: from [209.85.211.190] (HELO mail-yw0-f190.google.com) (209.85.211.190) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 07 Jun 2010 16:05:34 +0000 Received: by ywh28 with SMTP id 28so3245403ywh.28 for ; Mon, 07 Jun 2010 09:05:13 -0700 (PDT) MIME-Version: 1.0 Received: by 10.229.185.7 with SMTP id cm7mr2476142qcb.235.1275926711969; Mon, 07 Jun 2010 09:05:11 -0700 (PDT) Received: by 10.229.233.202 with HTTP; Mon, 7 Jun 2010 09:05:11 -0700 (PDT) In-Reply-To: <1C02D040F8560347822BE76ECDB76A18408F94B286@MAIL01.interprise.dk> References: <1C02D040F8560347822BE76ECDB76A18408F94B286@MAIL01.interprise.dk> Date: Mon, 7 Jun 2010 09:05:11 -0700 Message-ID: Subject: Re: Is ReplicationFactor values number of replicas or number of copies of data? From: Benjamin Black To: user@cassandra.apache.org Content-Type: text/plain; charset=ISO-8859-1 There is no 'master' so all copies are replicas. RF=1 means 1 node has the data, RF=2 means 2 do, etc. On Mon, Jun 7, 2010 at 4:16 AM, Per Olesen wrote: > Hi, > > I am unclear about what the ReplicationFactor value means. > > Does RF=1 mean that there is only one single node that has the data in the cluster (actually no replication), or, does it mean, that there are two copies of the data - one "actual" and one "replica" (as in "replicated one time")? > > I noticed, that I CAN start a node with RF=0, but I get UnavailableException when trying to insert, so I assume RF=0 is wrong then? > > Put another way: If I want my data to always live on exactly 2 nodes in the cluster, do I set RF=2 or RF=1? :-) > > /Per