Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id E6B4164FCD2 for ; Wed, 10 Sep 2008 14:38:42 -0300 (ADT) Received: from postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 31759-10 for ; Wed, 10 Sep 2008 14:38:32 -0300 (ADT) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from ey-out-2122.google.com (ey-out-2122.google.com [74.125.78.25]) by postgresql.org (Postfix) with ESMTP id 03F3564FCC4 for ; Wed, 10 Sep 2008 14:38:31 -0300 (ADT) Received: by ey-out-2122.google.com with SMTP id 6so1077296eyi.61 for ; Wed, 10 Sep 2008 10:38:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:cc:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=YitE6RhRIpth9V3XChn3PI+QLals0Al5Fm0Jia7FaBw=; b=iAAcWKFJ5D4hhBq+C0GexrqCuFc0kppCpR9CBw+aVmD05+duSRChEQMqVsxpPZFJp6 /DkwPvOqwt3huE4bgzzvndWMcy1oK3s3nV4gxtnZGBIiqRCK21bKAHWWwp7JE31FCccN 6jiifVaSzkhc00bTGS63yzv1dl50Yjzb8xQD4= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=cvU2viKvMBJK/x8Yet25AhGBALfysKAFLRqsYs4r6NXs4MVBZR8qTcvqmI47YD8GlP 9bK5Zf2GFiGTagh7MVzLFn9/erOoKq5P0+sVxhdXWePVKiZrPli4h/MtFze7VseXlf9N WuOlxjDHTOMHoLeyUOJkg+SjGCzXiCIW3rbJ8= Received: by 10.210.133.2 with SMTP id g2mr1775578ebd.163.1221068310314; Wed, 10 Sep 2008 10:38:30 -0700 (PDT) Received: by 10.210.72.10 with HTTP; Wed, 10 Sep 2008 10:38:30 -0700 (PDT) Message-ID: <70c01d1d0809101038q62e1f0ecnd2adb03ecf35ad41@mail.gmail.com> Date: Wed, 10 Sep 2008 10:38:30 -0700 From: "Mark Wong" To: "Scott Carey" Subject: Re: Effects of setting linux block device readahead size Cc: "Greg Smith" , "pgsql-performance@postgresql.org" , "Gabrielle Roth" , "Selena Deckelmann" In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <70c01d1d0809092353r4ae687a3ycf3d99d43a5680cf@mail.gmail.com> X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0 tagged_above=0 required=5 tests=none X-Spam-Level: X-Archive-Number: 200809/114 X-Sequence-Number: 31427 On Wed, Sep 10, 2008 at 9:26 AM, Scott Carey wrote: > How does that readahead tunable affect random reads or mixed random / > sequential situations? In many databases, the worst case scenarios aren't > when you have a bunch of concurrent sequential scans but when there is > enough random read/write concurrently to slow the whole thing down to a > crawl. How the file system behaves under this sort of concurrency > > I would be very interested in a mixed fio profile with a "background writer" > doing moderate, paced random and sequential writes combined with concurrent > sequential reads and random reads. The data for the other fio profiles we've been using are on the wiki, if your eyes can take the strain. We are working on presenting the data in a more easily digestible manner. I don't think we'll add any more fio profiles in the interest of moving on to doing some sizing exercises with the dbt2 oltp workload. We're just going to wrap up a couple more scenarios first and get through a couple of conference presentations. The two conferences in particular are the Linux Plumbers Conference, and the PostgreSQL Conference: West 08, which are both in Portland, Oregon. Regards, Mark