Return-Path: X-Original-To: apmail-hadoop-mapreduce-user-archive@minotaur.apache.org Delivered-To: apmail-hadoop-mapreduce-user-archive@minotaur.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id 3A0CADCB2 for ; Mon, 19 Nov 2012 15:01:58 +0000 (UTC) Received: (qmail 9665 invoked by uid 500); 19 Nov 2012 15:01:53 -0000 Delivered-To: apmail-hadoop-mapreduce-user-archive@hadoop.apache.org Received: (qmail 9258 invoked by uid 500); 19 Nov 2012 15:01:53 -0000 Mailing-List: contact user-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@hadoop.apache.org Delivered-To: mailing list user@hadoop.apache.org Received: (qmail 9239 invoked by uid 99); 19 Nov 2012 15:01:52 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 19 Nov 2012 15:01:52 +0000 X-ASF-Spam-Status: No, hits=2.2 required=5.0 tests=HTML_MESSAGE,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: local policy) Received: from [87.230.46.220] (HELO vwp3725.webpack.hosteurope.de) (87.230.46.220) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 19 Nov 2012 15:01:45 +0000 Received: from dslb-088-070-247-087.pools.arcor-ip.net ([88.70.247.87] helo=[192.168.2.107]); authenticated by vwp3725.webpack.hosteurope.de running ExIM with esmtpsa (TLS1.0:RSA_AES_128_CBC_SHA1:16) id 1TaSqj-0001Ag-0x; Mon, 19 Nov 2012 16:01:25 +0100 From: Kai Voigt Content-Type: multipart/alternative; boundary="Apple-Mail=_98E48E31-C30E-46B4-A2DD-E7D0BDE2EFEE" Message-Id: <5DD097F1-A97A-4C36-B8EF-2CB549EE32DB@123.org> Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Subject: Re: a question on NameNode Date: Mon, 19 Nov 2012 16:01:24 +0100 References: <106F2F9A-2A45-4B79-B392-4BBCCB2B04E5@123.org> To: user@hadoop.apache.org In-Reply-To: X-Mailer: Apple Mail (2.1499) X-bounce-key: webpack.hosteurope.de;k@123.org;1353337305;10690b45; X-Virus-Checked: Checked by ClamAV on apache.org --Apple-Mail=_98E48E31-C30E-46B4-A2DD-E7D0BDE2EFEE Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Am 19.11.2012 um 15:43 schrieb "Kartashov, Andy" = : > So, what if DN2 is down, i.e. it is not sending any blocks=92 report. = Then NN (I guess) will figure out that it has 2 blocks (3,4) that has no = home and that (without replication) it has no way of reconstructing the = file A.txt. It must spit the error then. One major feature of HDFS is its redundancy. Blocks are stored more than = once (three times by default), so chances are good that another DataNode = will have that block and report it during the safe mode phase. So the = file will be accessible. Kai --=20 Kai Voigt k@123.org --Apple-Mail=_98E48E31-C30E-46B4-A2DD-E7D0BDE2EFEE Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252
Am 19.11.2012 um = 15:43 schrieb "Kartashov, Andy" <Andy.Kartashov@mpac.ca>:
So, what if DN2 is down, i.e. it is not sending any = blocks=92 report.  Then NN (I guess) will figure out that it has 2 = blocks (3,4) that has no home and that (without replication) it has no = way of reconstructing the file A.txt. It must spit the error = then.

One major = feature of HDFS is its redundancy. Blocks are stored more than once = (three times by default), so chances are good that another DataNode will = have that block and report it during the safe mode phase. So the file = will be accessible.

Kai

-- 
Kai Voigt

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