From owner-freebsd-fs@FreeBSD.ORG Wed Jul 11 07:49:41 2012 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 8D3471065672 for ; Wed, 11 Jul 2012 07:49:41 +0000 (UTC) (envelope-from jusher71@yahoo.com) Received: from nm17-vm3.bullet.mail.ne1.yahoo.com (nm17-vm3.bullet.mail.ne1.yahoo.com [98.138.91.147]) by mx1.freebsd.org (Postfix) with SMTP id 1A9AE8FC0C for ; Wed, 11 Jul 2012 07:49:41 +0000 (UTC) Received: from [98.138.90.51] by nm17.bullet.mail.ne1.yahoo.com with NNFMP; 11 Jul 2012 07:49:34 -0000 Received: from [98.138.89.173] by tm4.bullet.mail.ne1.yahoo.com with NNFMP; 11 Jul 2012 07:49:34 -0000 Received: from [127.0.0.1] by omp1029.mail.ne1.yahoo.com with NNFMP; 11 Jul 2012 07:49:34 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 321567.77684.bm@omp1029.mail.ne1.yahoo.com Received: (qmail 7236 invoked by uid 60001); 11 Jul 2012 07:49:34 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1341992974; bh=v3IIEPkErMmRtsT+wsLsL9K2KECtuBczgjmeKZbHQtY=; h=X-YMail-OSG:Received:X-Mailer:Message-ID:Date:From:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=m53/HSe+RvYXv+1E/oJNmZim31sN0GTGlFgbalVDacuLG+LjS5scZhEpEIgtB4w7lnxsw/X/v9nfThxr2CvuY7rnQYFFSAQZqivGqEsGSr/WY/+dvws1PQYGh7TvKHKgmRCwtSdzA+qG7+CusBKvGMdGWDi//iaql/xjfMgNd7k= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:Message-ID:Date:From:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=XtyQTY3o1ZpE0EPba5QWGz0bKUTX4q0n00f2aAGYkf5bqpr3z9Y11aBAk7JCAKoKInXJk69qxn9VrPdgBnX428xIszlnCr0oXB56vvOfhJhsTDAGFzFmMjTl9hKBvEnoHQFmaS1HL5jJTbMKoq9Ymf9os3rqj5VfQ/NqIe+qG9c=; X-YMail-OSG: nHxfvCEVM1lfiEDPIwO2aNhLNaepZwAbwZK0TYmeYCP4gO4 WHUZ3qPSf5tva26OUf.HwKWCtCPkNZQVuKka4KmP1Q15Nu6qNvuZDUyKCXae 0Xj_KKFEvgZqxChmWBEhA2NvoJyAYZXIZycQT0_PKm4pCd.rbyoqrsN4R2nl lojdKZ4K.34uOR39M.UQhnushDrJMHvZU.ycG.gJKhiNYewENAg5J97WPAIQ tLWCglfEmYr_ogNyFh1ACDh8WFQED5DI4riqyofE8En3b1oHFsdR_8DxZfue Yom7cDhjxpbbH_9Ylnko_JmyAzo5eLjr.PuXEZpmETgaih8OzJcx.sj7juoB E_lK69AwoMF1.8LrpHs4gqga6giMV_ws4aUMks7pUdmcAq4hUSxPRLXrX24o WmnL3vecJNeyyrbUcnBQv.g-- Received: from [12.202.173.2] by web122503.mail.ne1.yahoo.com via HTTP; Wed, 11 Jul 2012 00:49:34 PDT X-Mailer: YahooMailClassic/15.0.8 YahooMailWebService/0.8.120.356233 Message-ID: <1341992974.53118.YahooMailClassic@web122503.mail.ne1.yahoo.com> Date: Wed, 11 Jul 2012 00:49:34 -0700 (PDT) From: Jason Usher To: Bob Friesenhahn In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Cc: freebsd-fs@freebsd.org Subject: Re: vdev/pool math with combined raidzX vdevs... X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 Jul 2012 07:49:41 -0000 =0AHello Bob,=0A=0A--- On Tue, 7/10/12, Bob Friesenhahn wrote:=0A=0A> > Am I really the only person worrying about the= =0A> interactive failure properties of combining vdevs into a=0A> pool ?=0A= > =0A> Yes.=A0 You are the only one.=A0 The strength of the=0A> individual = vdev is the primary determining factor of the=0A> strength of the pool.=0A= =0A=0AThanks for responding. So I must be mistaken, and the failure probab= ility of each vdev is not additive ? As I mentioned earlier in the thread,= I am not a probability person, nor would I trust my own calculations if I = tried.=0A=0ABecause if it is additive, combining vdevs erases about half of= the difference between raidz2 and raidz3, which I think is fairly signific= ant.=0A=0ACan we at least agree that it's not the same as a lone vdev ? If= I can destroy a vdev by blowing 4 disks in it, OR by blowing 4 disks in so= me other vdev, that's a higher risk than if it were alone...