Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ahECs-0007xU-Ct for pgsql-performance@arkaria.postgresql.org; Sat, 19 Mar 2016 10:34:06 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.84_2) (envelope-from ) id 1ahECr-0003Je-QX for pgsql-performance@arkaria.postgresql.org; Sat, 19 Mar 2016 10:34:05 +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_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1ahEBC-0001Tz-Ty for pgsql-performance@postgresql.org; Sat, 19 Mar 2016 10:32:22 +0000 Received: from mail-ig0-x236.google.com ([2607:f8b0:4001:c05::236]) by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.84_2) (envelope-from ) id 1ahEB6-0003nk-AW for pgsql-performance@postgresql.org; Sat, 19 Mar 2016 10:32:22 +0000 Received: by mail-ig0-x236.google.com with SMTP id nk17so39927659igb.1 for ; Sat, 19 Mar 2016 03:32:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc; bh=loOyo/QZYDzY/FF9nZNZ2/23lxprwWa4e0nDdrUp5Hw=; b=Qi7xAKE7+uy6TtSoZqBl+RM+hZxC9LufXVlQ6m8KeD0eZoXkRqgACVAVL5UupT8uAC SHZ8fYmxVrSPEt9nrESSKthJr0pkd9xxjJ5ggS7/Aswv1Ed1ttczzuM+QcR1GISwOqj/ QG5s8tn/R77b49NZ/IDG/tVVIVwW2+R+G5DUSDaP1Q1hl9t3ZsJUzEXBAP4CxSgbtNuT GoLOs46x/h4Vs1I4QQeRGRjoFb6150SqInB+2RE5Dt03mvSdvDIEDhmmayZrq3NvGLG+ bSLCyAfxjuvrwWajYjfWqpWqsxi2kL6ASzdYt6BqMX8lIBjXkCVzhsipFXGI7MrmTm2M Wu5w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc; bh=loOyo/QZYDzY/FF9nZNZ2/23lxprwWa4e0nDdrUp5Hw=; b=TSlMTi94cdubFgJD+bRoXiG0gUcqJtwNyYsViTMj3ZT1SmfGAo7gUaNRT0QdSB1a08 PMhHZO9NUdrg6B0gK5BRrsSso9PAAQEvahr08jm9wrx0T14bxD7I0D7GEIMRgjpYws7A yfOyB/Tx3C7fuWOepo6Zfne2FyxtTzDh/iwMgXIpT7hW7M9PvA9dm/6BOPleLlXFxqkB 888UnVBfdyKVWvQ/D3nmb+SgriiHSOWn0c1Cw/g70Q1aYzaSeRIS/WqFMxML/kAJMNJC 95FCreUtvg4S8j3+h2k2l/5tEXjjtz/2DdnIdLOp0SPGtNrgJxwWdwR9UlG1tvsLn4jO Bo9Q== X-Gm-Message-State: AD7BkJJVE7yLc/B4EKj8jXkiOnFEVOgX/yg61QNthsFirmRfrFyEY6naujKvIz0V8aYuuJ9FMGnri0MNS+y/eQ== MIME-Version: 1.0 X-Received: by 10.50.132.68 with SMTP id os4mr3547554igb.91.1458383533707; Sat, 19 Mar 2016 03:32:13 -0700 (PDT) Received: by 10.36.51.204 with HTTP; Sat, 19 Mar 2016 03:32:13 -0700 (PDT) In-Reply-To: References: Date: Sat, 19 Mar 2016 04:32:13 -0600 Message-ID: Subject: Re: Disk Benchmarking Question From: Scott Marlowe To: Dave Stibrany Cc: "pgsql-performance@postgresql.org" Content-Type: text/plain; charset=UTF-8 X-Pg-Spam-Score: -2.7 (--) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org On Sat, Mar 19, 2016 at 4:29 AM, Scott Marlowe wrote: > Given the size of your bonnie test set and the fact that you're using > RAID-10, the cache should make little or no difference. The RAID > controller may or may not interleave reads between all four drives. > Some do, some don't. It looks to me like yours doesn't. I.e. when > reading it's not reading all 4 disks at once, but just 2, 1 from each > pair. Point of clarification. It may be that if two processes are reading the data set at once you'd get a sustained individual throughput that matches what a single read can get. -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance