From user-return-17810-apmail-cassandra-user-archive=cassandra.apache.org@cassandra.apache.org Thu Jun 16 21:29:54 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 224B36426 for ; Thu, 16 Jun 2011 21:29:54 +0000 (UTC) Received: (qmail 78564 invoked by uid 500); 16 Jun 2011 21:28:39 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 78093 invoked by uid 500); 16 Jun 2011 21:28:38 -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 77883 invoked by uid 99); 16 Jun 2011 21:25:35 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 16 Jun 2011 21:25:35 +0000 X-ASF-Spam-Status: No, hits=-0.7 required=5.0 tests=FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,RFC_ABUSE_POST,SPF_PASS,T_TO_NO_BRKTS_FREEMAIL X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: domain of s5alye@gmail.com designates 209.85.214.172 as permitted sender) Received: from [209.85.214.172] (HELO mail-iw0-f172.google.com) (209.85.214.172) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 16 Jun 2011 21:25:30 +0000 Received: by iwn39 with SMTP id 39so1955105iwn.31 for ; Thu, 16 Jun 2011 14:25:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type:content-transfer-encoding; bh=cBu6OyCdiRsq4bty2mK+h3V9S7ACSupyXTMUiuiPzDU=; b=t5ZY9XXRWAn4tsHCvsBaiaE1AvyMMMo1c32TkWmKmmOOW1Siag+Dc0KkJz0WNntn1I pAPgTfVY9SQV/HK3eHBiIv/+k5ImPAOhvDY3AW7JIPi0EaHpi4vsLISz7vkJAEJma94K sCjKhQXZPLUf7MU3U/e1dWbGS7qXFJTUHaRc8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=gWoKweGPrYk5f/emqwCK31VIY0z4T+7sI3urdgvVPtuwLVL4TSQUkHC7+5DD9RYi3V yMwaM/a/mKpPOE3f1zkAAvr3U9zUmc72gMc6x8wReH+yVqp21jH2hglbJtV7kSMbDwlO i/1PvIi2UdoXD31xhbmZScCZux6NDWbOIInxY= MIME-Version: 1.0 Received: by 10.231.25.94 with SMTP id y30mr1183570ibb.61.1308259509015; Thu, 16 Jun 2011 14:25:09 -0700 (PDT) Received: by 10.231.35.198 with HTTP; Thu, 16 Jun 2011 14:25:08 -0700 (PDT) In-Reply-To: <56EF5399-4A4A-455A-BB4A-7EB70F81FE3E@thelastpickle.com> References: <56EF5399-4A4A-455A-BB4A-7EB70F81FE3E@thelastpickle.com> Date: Thu, 16 Jun 2011 17:25:08 -0400 Message-ID: Subject: Re: Force a node to form part of quorum From: A J To: user@cassandra.apache.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Virus-Checked: Checked by ClamAV on apache.org It would be great if Cassandra puts this on their roadmap. There is lot of durability benefits by incorporating dc awareness into the write consistency equation. MongoDB has this feature in their upcoming release: http://www.mongodb.org/display/DOCS/Data+Center+Awareness#DataCenterAwarene= ss-Tagging%28version1.9.1%29 On Thu, Jun 16, 2011 at 6:57 AM, aaron morton wro= te: > Short answer: =A0No. > Medium answer: No all nodes are equal. It could create a single point of > failure if a QUOURM could not be formed without a specific node. > Writes are sent to every replica. Reads with Read Repair enabled are also > sent to every replica. For reads the "closest" UP node as determined by t= he > snitch and possibly re-ordered by the Dynamic Snitch =A0is asked to retur= n the > actual data. This replica must respond for the request to complete. > If it's a question about maximising cache hits > see=A0https://github.com/apache/cassandra/blob/cassandra-0.8.0/conf/cassa= ndra.yaml#L308 > Cheers > > ----------------- > Aaron Morton > Freelance Cassandra Developer > @aaronmorton > http://www.thelastpickle.com > On 16 Jun 2011, at 05:58, A J wrote: > > Is there a way to favor a node to always participate (or never > participate) towards fulfillment of read consistency as well as write > consistency ? > > Thanks > AJ > >