Return-Path: Delivered-To: apmail-hadoop-zookeeper-user-archive@minotaur.apache.org Received: (qmail 40107 invoked from network); 31 Mar 2010 20:12:59 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 31 Mar 2010 20:12:59 -0000 Received: (qmail 40198 invoked by uid 500); 31 Mar 2010 20:12:59 -0000 Delivered-To: apmail-hadoop-zookeeper-user-archive@hadoop.apache.org Received: (qmail 40176 invoked by uid 500); 31 Mar 2010 20:12:59 -0000 Mailing-List: contact zookeeper-user-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: zookeeper-user@hadoop.apache.org Delivered-To: mailing list zookeeper-user@hadoop.apache.org Received: (qmail 40168 invoked by uid 99); 31 Mar 2010 20:12:59 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 31 Mar 2010 20:12:59 +0000 X-ASF-Spam-Status: No, hits=2.9 required=10.0 tests=HTML_MESSAGE,SPF_NEUTRAL X-Spam-Check-By: apache.org Received-SPF: neutral (athena.apache.org: local policy) Received: from [74.125.82.48] (HELO mail-ww0-f48.google.com) (74.125.82.48) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 31 Mar 2010 20:12:52 +0000 Received: by wwi18 with SMTP id 18so327444wwi.35 for ; Wed, 31 Mar 2010 13:12:31 -0700 (PDT) MIME-Version: 1.0 Received: by 10.216.62.147 with HTTP; Wed, 31 Mar 2010 13:12:30 -0700 (PDT) In-Reply-To: <4BB3AB57.6090709@darose.net> References: <4BB3AB57.6090709@darose.net> Date: Wed, 31 Mar 2010 13:12:30 -0700 Received: by 10.216.93.79 with SMTP id k57mr736826wef.161.1270066350746; Wed, 31 Mar 2010 13:12:30 -0700 (PDT) Message-ID: Subject: Re: the error From: Henry Robinson To: zookeeper-user@hadoop.apache.org Content-Type: multipart/alternative; boundary=0016e6d64544ad6cd204831e5d04 --0016e6d64544ad6cd204831e5d04 Content-Type: text/plain; charset=ISO-8859-1 Using two machines running ZK will actually decrease your reliability >> compared to using a single machine. Consider using one machine or three. >> > > ? > > Not meaning to pull the thread off-topic, but I don't understand why this > should be the case. Can you elaborate? > > With majority-based quorums, a 2 node ensemble will fail if either machine fails. This is the same as a 1 node ensemble - if one machine fails, the ensemble fails. But with the 2 nodes, you have (roughly) double the probability of experiencing a single failure, with the same failure profile. cheers, Henry > Thanks, > > DR > -- Henry Robinson Software Engineer Cloudera 415-994-6679 --0016e6d64544ad6cd204831e5d04--