Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1gcYwf-0001OR-SX for pgsql-performance@arkaria.postgresql.org; Thu, 27 Dec 2018 16:55:42 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.89) (envelope-from ) id 1gcYwe-00035y-Lp for pgsql-performance@arkaria.postgresql.org; Thu, 27 Dec 2018 16:55:40 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1gcYwe-00035m-Bg for pgsql-performance@lists.postgresql.org; Thu, 27 Dec 2018 16:55:40 +0000 Received: from mail-it1-x134.google.com ([2607:f8b0:4864:20::134]) by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1gcYwa-000897-UH for pgsql-performance@postgresql.org; Thu, 27 Dec 2018 16:55:39 +0000 Received: by mail-it1-x134.google.com with SMTP id z7so25277618iti.0 for ; Thu, 27 Dec 2018 08:55:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=telsasoft-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=nwv31VN3qBevpv3d3TL+tSOs6yyxdB7TLSXdLKAYzV8=; b=O0N2h5IgpN5p0XWF9ir8LH1qW3J0EWa6kyCh5d6zA7mt8V1SBXkWZCq05rbmslKNi5 qP5E5+TnotqpkujlTYPQZruPBTPxhsl6W0vr/+eDIsGIFRxi/VHSP8gUHzKq/YtdD9WE 73G30QjWDTgpMQSUqOJ65YT161tmG29wfCg7jWBYTyKwPySXEYY+GLm3cLqeC537DXtP xxMHE2pZldFfJ+2K3zP7WxGe9upR4hfE1nHr+mfxjIyiAWJrQ/vbQVKc+Tqa3eVPCtR2 TvgsulViQ+SCgdEqaeVGWKS6ydlemEtKc9eN3dsR/ngjxghjfAmBoR9e7lZpBPy8RY7c 6aeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=nwv31VN3qBevpv3d3TL+tSOs6yyxdB7TLSXdLKAYzV8=; b=WbVItBuoye3UcTfPi48geOY50Hjwldt05lpyWCI4hbC3NF53askTDPg6goDMCa4F0Z TXLi7QaYAkymqsy0gxwXJKGJNZJRX+pHq3jMCGCCrCbumSSUfrujk8HPL6738LXiVrDx SRIteKVYMiF1FD02SqjJeoXi6Y6nwaVbKJY04gZlOibbP/3UgK7EkX004DGL6ySKlKn7 WPmAm++eG6hcn6EGg2inWlgZb/y2DRUs8VfbCEmh6G847dTPb1thT8kxvTTRf2Tl5rsV CuPgg9QXIThBnpzeq7IBUmcsVUSMBazvdMuDhwvb1AgPptTOJUXQ2oi32uGM5JnPekKw zZRw== X-Gm-Message-State: AA+aEWZ9iq3YZtErWqMxNsaN/XsmiTVkV2ikCX+qxO35ID3I0HhPDH3f j7g7iYyx8cNofySB+zFZTXA+S1EFEAs= X-Google-Smtp-Source: ALg8bN6rHUhpsYSRN4O5rjyOR6OHPb/VMPwQXfPm00zrLJAf88Vu9FMXfU3qcSH2jhx6oyJcsEe+pQ== X-Received: by 2002:a24:2912:: with SMTP id p18mr15437405itp.16.1545929734928; Thu, 27 Dec 2018 08:55:34 -0800 (PST) Received: from pryzbyj (charmander.telsasoft.com. [50.244.222.1]) by smtp.gmail.com with ESMTPSA id k64sm14909663itb.7.2018.12.27.08.55.34 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Dec 2018 08:55:34 -0800 (PST) Received: by pryzbyj (Postfix, from userid 1000) id 79A7D8054BB; Thu, 27 Dec 2018 10:55:33 -0600 (CST) Date: Thu, 27 Dec 2018 10:55:33 -0600 From: Justin Pryzby To: Haroldo Kerry Cc: pgsql-performance@postgresql.org Subject: Re: PostgreSQL Read IOPS limit per connection Message-ID: <20181227165533.GS30382@telsasoft.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Precedence: bulk On Thu, Dec 27, 2018 at 02:44:55PM -0200, Haroldo Kerry wrote: > PostgreSQL 9.6.10 on x86_64-pc-linux-gnu (Debian 9.6.10-1.pgdg80+1), > Connected to SAN: Dell Compellent SC2020, with 7 x Samsung PM1633 SSDs > https://www.samsung.com/us/labs/pdfs/collateral/pm1633-prodoverview-2015.pdf, > RAID10+RAID5 configuration, 8GB Cache, read-write battery backed cache > enabled, connected via dedicated iSCSI switches and dedicated Ethernet > ports, in link aggregation mode (2x1Gbps max bandwidth). > I’m trying to figure out if PostgreSQL (PG) has some inherent limit on IOPS > per connection. postgres uses one server backend per client. > We tried to increase effective_io_size from 1 to 30, to no effect on > multiple tests. https://www.postgresql.org/docs/current/runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-ASYNC-BEHAVIOR => "Currently, this setting only affects bitmap heap scans." > Is this some inherent limitation of PG or am I misunderstanding something? It is a hsitoric limitation, but nowadays there's parallel query, which uses 2ndary "backend worker" processes. It's supported in v9.6 but much more versatile in v10 and v11. Justin