Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id 9628E36A390 for ; Wed, 16 Nov 2011 12:52:52 -0400 (AST) 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 02273-02 for ; Wed, 16 Nov 2011 16:52:46 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0-rc2 Received: from makus.postgresql.org (makus.postgresql.org [98.129.198.125]) by mail.postgresql.org (Postfix) with ESMTP id D5D1036A391 for ; Wed, 16 Nov 2011 12:52:46 -0400 (AST) Received: from ns2.gransy.com ([89.187.132.100] helo=elizabeth.gransy.com) by makus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1RQij7-0005Tr-KQ for pgsql-performance@postgresql.org; Wed, 16 Nov 2011 16:52:46 +0000 Received: from sq.gransy.com (localhost [127.0.0.1]) by elizabeth.gransy.com (Postfix) with ESMTP id EBA8215E44F8; Wed, 16 Nov 2011 17:52:31 +0100 (CET) Received: from 62.40.76.70 (proxying for unknown) (SquirrelMail authenticated user tv@fuzzy.cz) by sq.gransy.com with HTTP; Wed, 16 Nov 2011 17:52:31 +0100 Message-ID: <90891b62c1ea76f6e599616055e9cf88.squirrel@sq.gransy.com> In-Reply-To: References: <87e450fd65045c328f41e1b99a4029d5.squirrel@sq.gransy.com> <4EC30F05.6010901@fuzzy.cz> Date: Wed, 16 Nov 2011 17:52:31 +0100 Subject: Re: Slow queries / commits, mis-configuration or hardware issues? From: "Tomas Vondra" To: "Cody Caughlan" Cc: "Tomas Vondra" , pgsql-performance@postgresql.org User-Agent: SquirrelMail/1.4.21 MIME-Version: 1.0 Content-Type: text/plain;charset=utf-8 X-Priority: 3 (Normal) Importance: Normal Content-Transfer-Encoding: quoted-printable X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.9 tagged_above=-10 required=5 tests=BAYES_00=-1.9 X-Spam-Level: X-Archive-Number: 201111/196 X-Sequence-Number: 45707 On 16 Listopad 2011, 2:21, Cody Caughlan wrote: > How did you build your RAID array? Maybe I have a fundamental flaw / > misconfiguration. I am doing it via: > > $ yes | mdadm --create /dev/md0 --level=3D10 -c256 --raid-devices=3D4 > /dev/xvdb /dev/xvdc /dev/xvdd /dev/xvde > $ pvcreate /dev/md0 > $ vgcreate lvm-raid10 /dev/md0 > $ lvcreate -l 215021 lvm-raid10 -n lvm0 > $ blockdev --setra 65536 /dev/lvm-raid10/lvm0 > $ mkfs.xfs -f /dev/lvm-raid10/lvm0 > $ mkdir -p /data && mount -t xfs -o noatime /dev/lvm-raid10/lvm0 /data I'm not using EC2 much, and those were my first attempts with ephemeral storage, so this may be a stupid question, but why are you building a RAID-10 array on an ephemeral storage, anyway? You already have a standby, so if the primary instance fails you can easily failover. What are you going to do in case of a drive failure? With a server this i= s rather easy - just put there a new drive and you're done, but can you do that on EC2? I guess you can't do that when the instance is running, so you'll have to switch to the standby anyway, right? Have you ever tried this (how it affects the performance etc.)? So what additional protection does that give you? Wouldn't a RAID-0 be a better utilization of the resources? Tomas