From user-return-21428-apmail-cassandra-user-archive=cassandra.apache.org@cassandra.apache.org Fri Oct 7 13:21:36 2011 Return-Path: X-Original-To: apmail-cassandra-user-archive@www.apache.org Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id 2E4B89DD9 for ; Fri, 7 Oct 2011 13:21:36 +0000 (UTC) Received: (qmail 6685 invoked by uid 500); 7 Oct 2011 13:21:34 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 6615 invoked by uid 500); 7 Oct 2011 13:21:34 -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 6607 invoked by uid 99); 7 Oct 2011 13:21:33 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 07 Oct 2011 13:21:33 +0000 X-ASF-Spam-Status: No, hits=2.2 required=5.0 tests=FREEMAIL_FROM,HTML_MESSAGE,RCVD_IN_DNSWL_NONE,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: domain of peacepatriot@hotmail.com designates 65.55.116.99 as permitted sender) Received: from [65.55.116.99] (HELO blu0-omc3-s24.blu0.hotmail.com) (65.55.116.99) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 07 Oct 2011 13:21:25 +0000 Received: from BLU153-W1 ([65.55.116.74]) by blu0-omc3-s24.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675); Fri, 7 Oct 2011 06:21:05 -0700 Message-ID: Content-Type: multipart/alternative; boundary="_79c551fe-f9f0-4b38-8468-4de02b7b5180_" X-Originating-IP: [174.61.254.250] From: Anthony Wilcox To: Subject: Immutable CFs and read consistency Date: Fri, 7 Oct 2011 06:21:04 -0700 Importance: Normal MIME-Version: 1.0 X-OriginalArrivalTime: 07 Oct 2011 13:21:05.0149 (UTC) FILETIME=[F784B2D0:01CC84F3] --_79c551fe-f9f0-4b38-8468-4de02b7b5180_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable We have a Column Family that is immutable (no updates after the first write= ). Suppose we use RF=3D2 and W=3D1. Do we still need R=3D2=2C so that R+W= >RF? Or is it sufficient to have R=3D1? My guess is yes=2C R=3D1 is suffi= cient since if it reads a row=2C the row has to be correct: it can't get st= ale data. But can it get NO data? That is=2C with R=3D1 might cassandra= look on one of the two nodes=2C find no data there=2C and prematurely give= up? In other words=2C does R apply only to (possibly failed) read attempt= s or only to successful reads? Thanks=2C Anthony = --_79c551fe-f9f0-4b38-8468-4de02b7b5180_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
We have a Column Family that is immutable (no updates after the first write= ). =3B Suppose we use RF=3D2 and W=3D1. =3B Do we still need R=3D2= =2C so that R+W>=3BRF? =3B Or is it sufficient to have R=3D1? =3B= My guess is yes=2C R=3D1 is sufficient since if it reads a row=2C the row = has to be correct: it can't get stale data.  =3B  =3B But can it ge= t NO data? That is=2C with R=3D1 might cassandra look on one of the two nod= es=2C find no data there=2C and prematurely give up? =3B In other words= =2C does R apply only to (possibly failed) read attempts or only to success= ful reads?

 =3BThanks=2C Anthony
= --_79c551fe-f9f0-4b38-8468-4de02b7b5180_--