Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1ZXFeV-0007mH-MS for pgsql-hackers@arkaria.postgresql.org; Wed, 02 Sep 2015 21:33:07 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.84) (envelope-from ) id 1ZXFeV-0003nM-8Z for pgsql-hackers@arkaria.postgresql.org; Wed, 02 Sep 2015 21:33:07 +0000 Received: from makus.postgresql.org ([2001:4800:1501:1::229]) by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256) (Exim 4.84) (envelope-from ) id 1ZXFdA-0001Aq-AC for pgsql-hackers@postgresql.org; Wed, 02 Sep 2015 21:31:44 +0000 Received: from mx-out.zmailcloud.com ([192.198.85.98] helo=mx-out-1.zmailcloud.com) by makus.postgresql.org with esmtp (Exim 4.84) (envelope-from ) id 1ZXFd7-0007Zw-ME for pgsql-hackers@postgresql.org; Wed, 02 Sep 2015 21:31:43 +0000 Received: from smtp.01.com (smtp.01.com [10.10.0.43]) by mx-out-1.zmailcloud.com (Postfix) with ESMTP id 09A16563D87; Wed, 2 Sep 2015 16:31:41 -0500 (CDT) Received: from localhost (localhost [127.0.0.1]) by smtp-out-1.01.com (Postfix) with ESMTP id 00D68A039B; Wed, 2 Sep 2015 16:31:40 -0500 (CDT) X-Virus-Scanned: amavisd-new at smtp-out-1.01.com Received: from smtp.01.com ([127.0.0.1]) by localhost (smtp-out-1.01.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hnXgYWR8DFkl; Wed, 2 Sep 2015 16:31:40 -0500 (CDT) Received: from smtp.01.com (localhost [127.0.0.1]) by smtp-out-1.01.com (Postfix) with ESMTP id BFECCA03C9; Wed, 2 Sep 2015 16:31:40 -0500 (CDT) Received: from localhost (localhost [127.0.0.1]) by smtp-out-1.01.com (Postfix) with ESMTP id 963AAA03C7; Wed, 2 Sep 2015 16:31:40 -0500 (CDT) X-Virus-Scanned: amavisd-new at smtp-out-1.01.com Received: from smtp.01.com ([127.0.0.1]) by localhost (smtp-out-1.01.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id U2VX4TFOvsdc; Wed, 2 Sep 2015 16:31:40 -0500 (CDT) Received: from [172.47.23.104] (50-0-190-244.dsl.dynamic.fusionbroadband.com [50.0.190.244]) by smtp-out-1.01.com (Postfix) with ESMTPSA id 02F99A039B; Wed, 2 Sep 2015 16:31:39 -0500 (CDT) Subject: Re: Allow a per-tablespace effective_io_concurrency setting To: Tomas Vondra , pgsql-hackers@postgresql.org References: <20141206130828.GA1314@momjian.us> <20141209204337.GC24488@momjian.us> <55AA2469.20306@dalibo.com> <55AA27C3.7060009@dalibo.com> <20150902135351.GA5286@alap3.anarazel.de> <55E76950.2070403@2ndquadrant.com> From: Josh Berkus Organization: PostgreSQL Experts Inc. Message-ID: <55E76AB7.4030306@agliodbs.com> Date: Wed, 2 Sep 2015 14:31:35 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Pg-Spam-Score: -2.6 (--) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-hackers Precedence: bulk Sender: pgsql-hackers-owner@postgresql.org On 09/02/2015 02:25 PM, Tomas Vondra wrote: > > As I explained, spindles have very little to do with it - you need > multiple I/O requests per device, to get the benefit. Sure, the DBAs > should know how many spindles they have and should be able to determine > optimal IO depth. But we actually say this in the docs: My experience with performance tuning is that values above 3 have no real effect on how queries are executed. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers