Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id 65524B5DE1E for ; Thu, 3 Nov 2011 12:53:54 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 91135-01-7 for ; Thu, 3 Nov 2011 15:53:48 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0-rc2 Received: from mail-ey0-f174.google.com (mail-ey0-f174.google.com [209.85.215.174]) by mail.postgresql.org (Postfix) with ESMTP id 9F6FAB5DDE4 for ; Thu, 3 Nov 2011 12:53:35 -0300 (ADT) Received: by eye27 with SMTP id 27so1254856eye.19 for ; Thu, 03 Nov 2011 08:53:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=tkBQgiGne5PHkZVIGnjqMQHGf7uH+2sgEvZEVbu35fk=; b=xdo51wgJHBIXsVGSoWlhG0rwfrShRvgp0qQal/jEur94pgkgZO/BktZ+LTiSZZr/ky TmS2sWy2NyJ9oZA/ifk0t1JeeyjavClx0veMonOkJuBFm+vu98sGdzpkh58/wsC5e4NJ xiDOVfNBKO0PTyDVvc1TYjC1JPbkz9ED5abT4= Received: by 10.14.23.194 with SMTP id v42mr1021533eev.174.1320335613181; Thu, 03 Nov 2011 08:53:33 -0700 (PDT) Received: from [192.168.73.63] (5357DA75.cm-6-8d.dynamic.ziggo.nl. [83.87.218.117]) by mx.google.com with ESMTPS id x12sm16884159eef.9.2011.11.03.08.52.59 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 03 Nov 2011 08:53:00 -0700 (PDT) Message-ID: <4EB2B8D0.8030509@gmail.com> Date: Thu, 03 Nov 2011 16:52:48 +0100 From: Yeb Havinga User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1 MIME-Version: 1.0 To: Magnus Hagander CC: Kevin Grittner , "pgsql-performance@postgresql.org" Subject: Re: Intel 710 pgbench write latencies References: <4EB14002.1020306@gmail.com> <4EB1081A0200002500042927@gw.wicourts.gov> <4EB15BFE.9000309@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.899 tagged_above=-10 required=5 tests=BAYES_00=-1.9, FREEMAIL_FROM=0.001 X-Spam-Level: X-Archive-Number: 201111/53 X-Sequence-Number: 45564 On 2011-11-02 16:06, Magnus Hagander wrote: > On Wed, Nov 2, 2011 at 16:04, Yeb Havinga wrote: >> On 2011-11-02 15:06, Kevin Grittner wrote: >>> Yeb Havinga wrote: >>> >>>> I'm now contemplating not using the 710 at all. Why should I not >>>> buy two 6Gbps SSDs without supercap (e.g. Intel 510 and OCZ Vertex >>>> 3 Max IOPS) with a IO controller+BBU? >>> Wouldn't the data be subject to loss between the time the IO >>> controller writes to the SSD and the time it makes it from buffers >>> to flash RAM? >> Good question. My guess would be no, if the raid controller does >> 'write-throughs' on the attached disks, and the SSD's don't lie about when >> they've written to RAM. > Doesn't most SSDs without supercaps lie about the writes, though? > I happened to have a Vertex 3, no supercap, available to test this with diskchecker. On a ext4 filesystem (just mounted with noatime, not barriers=off), this happenend: # /root/diskchecker.pl -s 192.168.73.1 verify testfile verifying: 0.00% verifying: 30.67% verifying: 78.97% verifying: 100.00% Total errors: 0 So I guess that's about as much as I can test without actually hooking it behind a hardware controller and test that. I will soon test the 3ware 9750 with Vertex 3 and Intel 510 - both in the 3ware's ssd compatibility list. More info from testing software raid 1: - with lvm mirroring, discards / trim go through to the disks. This is where the Intel is fast enough, but the vertex 2 pro is busy for ~ 10 seconds. -- Yeb