Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1ZCZ9d-00051d-AS for pgsql-performance@arkaria.postgresql.org; Tue, 07 Jul 2015 20:07:45 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.84) (envelope-from ) id 1ZCZ9c-0004hY-KK for pgsql-performance@arkaria.postgresql.org; Tue, 07 Jul 2015 20:07:44 +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 1ZCZ7B-0002N5-2O for pgsql-performance@postgresql.org; Tue, 07 Jul 2015 20:05:13 +0000 Received: from mail-wi0-x22c.google.com ([2a00:1450:400c:c05::22c]) by makus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.84) (envelope-from ) id 1ZCZ78-0002bp-Oj for pgsql-performance@postgresql.org; Tue, 07 Jul 2015 20:05:11 +0000 Received: by wiclp1 with SMTP id lp1so61291716wic.0 for ; Tue, 07 Jul 2015 13:05:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:message-id:date:from:reply-to:user-agent:mime-version:to:cc :subject:references:in-reply-to:content-type :content-transfer-encoding; bh=2vmbdAgxGFgxCxBJN0jAzy1LAS8DIJ2lrOejHtXbNYk=; b=Ow2n03oGTeDgmCdDPDf3ftzk06lmTEmrZZMZCw9kYKZWj8vMj3cox4dOh5Ka0U3s2B aP4lPIyc7Z5DVcmzWHD8cHaCOTu6b3tAUNVmZLyzoKiL2Z1M5WLeH76knXsm1XItSyzo 8+E91g1GLsTCqcqCQFSmEScfRweu7hgbMpSMukpszj1vLrfNwUmZ+HTra5fMwL7oQX+k rFoIz3dEvjr9n4jJhl1r5vz4oMoP76j0aRtZqfiXbHUx7zja/G/YNLr7Amhbkky8Sqcw 9MesnPAx8FQ4Rls2oKwmVbH+X1q06hD8RgxzIPHO3STpA784hsM8C7Is0QG4wMyaUaIf YXOg== X-Received: by 10.194.77.144 with SMTP id s16mr12099286wjw.145.1436299509453; Tue, 07 Jul 2015 13:05:09 -0700 (PDT) Received: from [192.168.1.110] (dsl-hkibrasgw1-58c38f-82.dhcp.inet.fi. [88.195.143.82]) by mx.google.com with ESMTPSA id bg6sm35034455wjc.13.2015.07.07.13.05.07 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Jul 2015 13:05:08 -0700 (PDT) Message-ID: <559C30F2.3000703@iki.fi> Date: Tue, 07 Jul 2015 23:05:06 +0300 From: Heikki Linnakangas Reply-To: hlinnaka@iki.fi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.7.0 MIME-Version: 1.0 To: "Graeme B. Bell" CC: "Wes Vaske (wvaske)" , "pgsql-performance@postgresql.org" Subject: Re: New server: SSD/RAID recommendations? References: <31701C89A44B714FB8D242F806E7286C5AED32FA@NTXBOIMBX01.micron.com> <31701C89A44B714FB8D242F806E7286C5AED33EB@NTXBOIMBX01.micron.com> <31701C89A44B714FB8D242F806E7286C5AED372E@NTXBOIMBX01.micron.com> <559BE965.7090609@iki.fi> <31701C89A44B714FB8D242F806E7286C5AED3892@NTXBOIMBX01.micron.com> <559C2E31.4060107@iki.fi> In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Pg-Spam-Score: -2.4 (--) 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 07/07/2015 10:59 PM, Graeme B. Bell wrote: > Cache flushing isn't an atomic operation though. Even if the ordering > is right, you are likely to have a partial fsync on the disk when the > lights go out - isn't your FS still corrupt? If the filesystem is worth its salt, no. Journaling filesystems for example rely on the journal to work around that problem, and there are other mechanisms. PostgreSQL has exactly the same problem and uses the WAL to solve it. - Heikki -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance