Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 5C7992E2F87 for ; Thu, 27 Dec 2007 13:05:44 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 85111-01-10 for ; Thu, 27 Dec 2007 13:05:38 -0400 (AST) Received: from mx00.pub.collaborativefusion.com (mx00.pub.collaborativefusion.com [206.210.89.199]) by postgresql.org (Postfix) with ESMTP id 787F32E3584 for ; Thu, 27 Dec 2007 12:54:46 -0400 (AST) Received: from vanquish.pitbpa0.priv.collaborativefusion.com (vanquish.pitbpa0.priv.collaborativefusion.com [192.168.2.61]) (SSL: TLSv1/SSLv3,256bits,AES256-SHA) by wingspan with esmtp; Thu, 27 Dec 2007 11:54:45 -0500 id 00056407.4773D8D5.00000FB0 Date: Thu, 27 Dec 2007 11:54:44 -0500 From: Bill Moran To: Mark Mielke Cc: david@lang.hm, Florian Weimer , Fernando Hevia , 'pgsql-performance' Subject: Re: With 4 disks should I go for RAID 5 or RAID 10 Message-Id: <20071227115444.07a9af3f.wmoran@collaborativefusion.com> In-Reply-To: <4773C3AE.1060602@mark.mielke.cc> References: <0f8201c847f6$08e15090$8f01010a@iptel.com.ar> <87zlvxnpkl.fsf@mid.deneb.enyo.de> <4772CA58.5050406@mark.mielke.cc> <4772CE34.2040608@mark.mielke.cc> <20071226171105.889f6146.wmoran@collaborativefusion.com> <4772D3DA.10302@mark.mielke.cc> <20071227085009.94ea3bef.wmoran@collaborativefusion.com> <4773C3AE.1060602@mark.mielke.cc> Organization: Collaborative Fusion X-Mailer: Sylpheed 2.4.7 (GTK+ 2.12.1; i386-portbld-freebsd6.2) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200712/417 X-Sequence-Number: 28233 In response to Mark Mielke : > Bill Moran wrote: > > In response to Mark Mielke : > > > > > >> Bill Moran wrote: > >> > >>> I'm fairly sure that FreeBSD's GEOM does. Of course, it couldn't be doing > >>> consistency checking at that point. > >>> > >> According to this: > >> > >> http://www.freebsd.org/cgi/man.cgi?query=gmirror&apropos=0&sektion=8&manpath=FreeBSD+6-current&format=html > >> > >> There is a -b (balance) option that seems pretty clear that it does not > >> read from all drives if it does not have to: > >> > > > > >From where did you draw that conclusion? Note that the "split" algorithm > > (which is the default) divides requests up among multiple drives. I'm > > unclear as to how you reached a conclusion opposite of what the man page > > says -- did you test and find it not to work? > > > Perhaps you and I are speaking slightly different languages? :-) When I > say "does not read from all drives", I mean "it will happily read from > any of the drives to satisfy the request, and allows some level of > configuration as to which drive it will select. It does not need to read > all of the drives to satisfy the request." Ahh ... I did misunderstand you. -- Bill Moran Collaborative Fusion Inc. http://people.collaborativefusion.com/~wmoran/ wmoran@collaborativefusion.com Phone: 412-422-3463x4023