Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.84_2) (envelope-from ) id 1aiNXZ-0000K4-Ol for pgsql-performance@arkaria.postgresql.org; Tue, 22 Mar 2016 14:44:13 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.84_2) (envelope-from ) id 1aiNXZ-0001g2-73 for pgsql-performance@arkaria.postgresql.org; Tue, 22 Mar 2016 14:44:13 +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_2) (envelope-from ) id 1aiNXW-0001dx-GD for pgsql-performance@postgresql.org; Tue, 22 Mar 2016 14:44:10 +0000 Received: from mail-oi0-x22e.google.com ([2607:f8b0:4003:c06::22e]) by makus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.84_2) (envelope-from ) id 1aiNXU-0004E5-6l for pgsql-performance@postgresql.org; Tue, 22 Mar 2016 14:44:09 +0000 Received: by mail-oi0-x22e.google.com with SMTP id i17so10155153oib.1 for ; Tue, 22 Mar 2016 07:44:07 -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; bh=MVxyUB984/iy8SiVE/jABJnWQrcdDkXbTl5ytzPuGxo=; b=IA27WaUThheR00YvsbXRMCl6ygC5Bm1Yjqisco9PXvB7Kkahsvvkns7hltvP3lwNK7 Nnwx17pF1vTeqspGuq0gcVuIx/Das0ivdvuMIzBFKUBdmNi3B6w1ibujSFSNBcJa07n/ vOgmFlubtxIL435F4gbnS6Z8EtMYUxwNqGn+KLr6Z2Xc+V7B3KKmFuaokdRveSch8puv 3vUUtiwO6EhS/ZScaXWkveHLCmyQPYrvIuaqxH9687g8Hyulm7QnlPxNirLhqAzNqoSg qZJj3TlBh7q91XTgg1GsCkHJX+ZMMLwrKBkB90OlBgMYD90d2nZMH0oNC8aPMPI7KTBL yXcQ== 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; bh=MVxyUB984/iy8SiVE/jABJnWQrcdDkXbTl5ytzPuGxo=; b=B/02Ueft4iyjyASrBF4P8uIMWdlvn8ZyKPXEac2LQcl6WrbxPXjPAcmfWfRaeUPYge ue7bS27bCeJhH+X9qQBkowRhJUga41wkGb2OkqeT8bLv98wiaVWbui8B1Xy5ZgKMqsvE /8WnEsTcvYbRl74M5s7+mLpx+COFld15Hw9H0NAGIkFkgPVZeeMPSbmyzLXo83L6kNGh /hNu8sP06uicm4xbVSW/wkCFiL4/9PJZocMQnwl8LYC66GYTsTSzgjrKhD/B4CGGUy0/ V5WcXq9fiM7473bDMVV4wP5cyEuYSp7/sdrnnbZIkzjmSeIsG/rYVem1ivqUrE3FS/j3 fnTQ== X-Gm-Message-State: AD7BkJJ5XRuOLjajlQE4t6prx8MN0pTmhCmI0iN3nae4Z1XRoArwC+0cqYUUAvsERQb6sGGJu6TuMYpSDa4hnQ== MIME-Version: 1.0 X-Received: by 10.202.186.193 with SMTP id k184mr20205667oif.66.1458657847291; Tue, 22 Mar 2016 07:44:07 -0700 (PDT) Received: by 10.76.141.9 with HTTP; Tue, 22 Mar 2016 07:44:07 -0700 (PDT) In-Reply-To: References: Date: Tue, 22 Mar 2016 10:44:07 -0400 Message-ID: Subject: Re: Disk Benchmarking Question From: Dave Stibrany To: "pgsql-performance@postgresql.org" Content-Type: multipart/alternative; boundary=001a113ce218d636b1052ea43e14 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 --001a113ce218d636b1052ea43e14 Content-Type: text/plain; charset=UTF-8 Thanks for the feedback guys. I'm looking forward to the day when we upgrade to SSDs. For future reference, the bonnie++ numbers I was referring to are: Size: 63G Sequential Output: ------------------------ 396505 K/sec % CPU 21 Sequential Input: ------------------------ 401117 K/sec % CPU 21 Random Seeks: ---------------------- 650.7 /sec % CPU 25 I think a lot of my confusion resulted from expecting sequential reads to be 4x the speed of a single disk because the disks are in RAID10. I'm thinking now that the 4x only applies to random reads. On Sat, Mar 19, 2016 at 6:32 AM, Scott Marlowe wrote: > 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. > -- *THIS IS A TEST* --001a113ce218d636b1052ea43e14 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Thanks for the feedback guys. I'm looking forward to t= he day when we upgrade to SSDs.

For future reference, th= e bonnie++ numbers I was referring to are:=C2=A0

S= ize: 63G

Sequential Output:=C2=A0
------------------------
396505 K/sec
% CPU 21

Sequential Input:=C2=A0
------------------= ------
401117 K/sec=
% CPU 21

Random Seeks:
= ----------------------
650.7 /sec
% CPU 25
I think a lot of my confusion resulted from expecting sequenti= al reads to be 4x the speed of a single disk because the disks are in RAID1= 0. I'm thinking now that the 4x only applies to random reads.

On Sat, Mar 19,= 2016 at 6:32 AM, Scott Marlowe <scott.marlowe@gmail.com> wrote:
On Sat, Mar 1= 9, 2016 at 4:29 AM, Scott Marlowe <scott.marlowe@gmail.com> wrote:

> Given the size of your bonnie test set and the fact that you're us= ing
> 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. w= hen
> reading it's not reading all 4 disks at once, but just 2, 1 from e= ach
> pair.

Point of clarification. It may be that if two processes are reading<= br> the data set at once you'd get a sustained individual throughput that matches what a single read can get.



--
THIS IS A TEST
--001a113ce218d636b1052ea43e14--