Return-Path: Delivered-To: apmail-hadoop-common-dev-archive@www.apache.org Received: (qmail 82182 invoked from network); 16 Nov 2009 20:46:22 -0000 Received: from hermes.apache.org (HELO mail.apache.org) (140.211.11.3) by minotaur.apache.org with SMTP; 16 Nov 2009 20:46:22 -0000 Received: (qmail 48713 invoked by uid 500); 16 Nov 2009 20:46:21 -0000 Delivered-To: apmail-hadoop-common-dev-archive@hadoop.apache.org Received: (qmail 48324 invoked by uid 500); 16 Nov 2009 20:46:20 -0000 Mailing-List: contact common-dev-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: common-dev@hadoop.apache.org Delivered-To: mailing list common-dev@hadoop.apache.org Received: (qmail 48098 invoked by uid 500); 16 Nov 2009 20:46:19 -0000 Delivered-To: apmail-hadoop-core-dev@hadoop.apache.org Received: (qmail 48022 invoked by uid 99); 16 Nov 2009 20:46:19 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 16 Nov 2009 20:46:19 +0000 X-ASF-Spam-Status: No, hits=-2.6 required=5.0 tests=AWL,BAYES_00,HTML_MESSAGE X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: local policy) Received: from [67.195.22.98] (HELO web112120.mail.gq1.yahoo.com) (67.195.22.98) by apache.org (qpsmtpd/0.29) with SMTP; Mon, 16 Nov 2009 20:46:17 +0000 Received: (qmail 76856 invoked by uid 60001); 16 Nov 2009 20:45:56 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1258404356; bh=/gYgTc33rpUIXgZ27hp5LHxz1sHznJMVjJYIp9EOrwE=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type; b=Wcz9/RqHfrmC4q4LFecNDF52f3/AhLRP3EwNcEjvUh85rSynUZzjyhivHKTDtidTXXPepiusBlYszmYhVDc9S+XZ5cQ2vjB0ddbRMGSxgwCqC0xiYUGu5f5OpOr5bvbkAowG0dv/9/0y9QQW5KqRDZAdVC+gtrIqZJ39Yya+mhg= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type; b=nD6Jjuk/UNKKIPFmZsGVTVveIK+CkJ46LFArUHD6O8c7vRSPZ/av5JSW8XMpL0c/dB7JVx/0/zisGzF3FeBo/RhbK+gvR1bvJtiPfeAFSmMKDJMrVQrhmKt5qeIOWrvX97G4a/gvYEcKPJuYhDiUugup1V8dmd0XwB/1vskFQ0U=; Message-ID: <240158.76395.qm@web112120.mail.gq1.yahoo.com> X-YMail-OSG: hp8Siq8VM1kEpcvoYdcdQSMbfBspM5zUo2tWbh0C46TjELxtuZDmXrxuzWFW3azIxp3IlwhJJLO_rPMa0luBFDRAJOCf2ZBfkXhECTyt6C2Y04uwXG5JxWtELrAoCRb0Dd_LV36J9F_zNgIA0X9m9IE29lRCWYOojllPjkHsyfr37Hb8hF3FxbgBL2p5_nRlljsjpDvapO627EiVrl7ULppl0Mlkp6iOd_v0Qy8_y6Qoc0J5Aa4HG6X52kTHaqxkug-- Received: from [64.172.17.3] by web112120.mail.gq1.yahoo.com via HTTP; Mon, 16 Nov 2009 12:45:56 PST X-Mailer: YahooMailClassic/8.1.6 YahooMailWebService/0.7.361.4 Date: Mon, 16 Nov 2009 12:45:56 -0800 (PST) From: Steve Gao Subject: What's different of 1)namenode metadata 2)image and 3)edit logs? To: general@hadoop.apache.org Cc: core-user@hadoop.apache.org, core-dev@hadoop.apache.org MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1555827857-1258404356=:76395" --0-1555827857-1258404356=:76395 Content-Type: text/plain; charset=us-ascii What are the differences between the 3 concepts: (1) namenode metadata, (2) namenode image, and (3) edit logs? BTW,I know the secondary namenode backups namenode data. I was told that there is another daemon which also backups meta data . Is that true? What is the daemon? Thanks. --0-1555827857-1258404356=:76395--