Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 44D4064FF8E for ; Thu, 28 Aug 2008 19:03:28 -0300 (ADT) Received: from postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 37958-02 for ; Thu, 28 Aug 2008 19:03:21 -0300 (ADT) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from rv-out-0506.google.com (rv-out-0506.google.com [209.85.198.227]) by postgresql.org (Postfix) with ESMTP id 516CC64FD09 for ; Thu, 28 Aug 2008 19:03:25 -0300 (ADT) Received: by rv-out-0506.google.com with SMTP id b25so755423rvf.43 for ; Thu, 28 Aug 2008 15:03:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:cc:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=hUG4rrq55hULk9WA9eLfDq0vdrUtFWC8kttNh7jtbFE=; b=eSfqdkKdU4re5TkTXQ9iRBU8TekQgnb4ZkjDG4Utb4t40s+sFOkNYrffwTLWwDOlIm 3oOGHrn/Rfzb+IR2eqtJb7oX6W7EpkHQ5UcQUWqqBi74gjJQV0uNNhFXG99tG1UsEG8G TSiYMVIvQIFlO+PltqEIIH3xYKX8eCDOqVAng= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=OeAXEEhB+fjG1nIAFJLLjbu1b1Db0H2BTDxsoc+5DKRCPOumCXZGLMgRBKKeSFkKRW bntQRRCHjAYyBsVoa4wqk/evA2rmJ1+nIIhMpXdAEU6FA5V8J0t8y4okq/h6KJbQttKu AHGIhOlfiwvoH86QEzcjhZRumHGuij5hDHBoU= Received: by 10.140.199.3 with SMTP id w3mr1075465rvf.67.1219961004095; Thu, 28 Aug 2008 15:03:24 -0700 (PDT) Received: by 10.141.197.1 with HTTP; Thu, 28 Aug 2008 15:03:24 -0700 (PDT) Message-ID: Date: Thu, 28 Aug 2008 16:03:24 -0600 From: "Scott Marlowe" To: cluster Subject: Re: Best hardware/cost tradoff? Cc: pgsql-performance@postgresql.org In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <064701c90949$51d117d0$8f01010a@iptel.com.ar> <48B709A5.3090906@emolecules.com> X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0 tagged_above=0 required=5 tests=none X-Spam-Level: X-Archive-Number: 200808/394 X-Sequence-Number: 31275 On Thu, Aug 28, 2008 at 3:29 PM, cluster wrote: > Thanks for all your replies! They are enlightening. I have some additional > questions: > > 1) Would you prefer > a) 5.4k 2" SATA RAID10 on four disks or > b) 10k 2" SAS RAID1 on two disks? > (Remember the lots (!) of random reads) I'd lean towards 4 disks in RAID-10. Better performance when > 1 read is going on. Similar commit rates to the two 10k drives. Probably bigger drives too, right? Always nice to have room to work in. > 2) Should I just make one large partition of my RAID? Does it matter at all? Probably. With more disks it might be advantageous to split out two drives into RAID-10 for pg_xlog. with 2 or 4 disks, splitting off two for pg_xlog might slow down the data partition more than you gain from a separate pg_xlog drive set. > 3) Will I gain much by putting the OS on a saparate disk, not included in > the RAID? (The webserver and database would still share the RAID - but I > guess the OS will cache my (small) web content in RAM anyway). The real reason you want your OS on a different set of drives is that it allows you to reconfigure your underlying RAID array as needed without having to reinstall the whole OS again. Yeah, logging to /var/log will eat some bandwidth on your RAID as well, but the ease of maintenance is why I do it as much as anything. A lot of large servers support 2 fixed drives for the OS and a lot of removeable drives hooked up to a RAID controller for this reason.