From owner-freebsd-hackers@FreeBSD.ORG Sat Jun 6 20:16:33 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E31871065673 for ; Sat, 6 Jun 2009 20:16:33 +0000 (UTC) (envelope-from fjwcash@gmail.com) Received: from mail-gx0-f207.google.com (mail-gx0-f207.google.com [209.85.217.207]) by mx1.freebsd.org (Postfix) with ESMTP id 9D07C8FC13 for ; Sat, 6 Jun 2009 20:16:33 +0000 (UTC) (envelope-from fjwcash@gmail.com) Received: by gxk3 with SMTP id 3so2966172gxk.19 for ; Sat, 06 Jun 2009 13:16:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type :content-transfer-encoding; bh=a/fCRP40s8GHDFsKaEd2Z9GZuzfeLKdTdZIBmblBbTw=; b=Izc6Uc2R06IDBzz/cyXeYv8VJ9E9awbjJTNHckbpc0BE4A4TXLzxsl71Fyyomkk+MJ M1gKFjZpUfKJUhKwrAzKOaSM9gpIVDqxkV5nFm1aEeD8tR0sx0Dk03a/sQjclgo1+9F4 vyJvX5e5dGe7m7IcDMZFfYUDk8VkdxH8VPC0U= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=piniRMPZmJ1TLURjUdPJE6wS4cgZj3l+IRdUYXZpmgNB7uAezJrvUtsup4fmLHwYjo nNkpZeuAxnVD4DmsB2Y0gN2EWJreD1lmFzaPvPMvDfg+JPpi0yozBqpn5p1Ys6irbl59 +O9lSa5NzJxE7xvmp8l0zaNZ5oG16cZEwGsHM= MIME-Version: 1.0 Received: by 10.151.135.8 with SMTP id m8mr9053478ybn.185.1244319393021; Sat, 06 Jun 2009 13:16:33 -0700 (PDT) In-Reply-To: References: <20090530175239.GA25604@logik.internal.network> <20090530144354.2255f722@bhuda.mired.org> <20090530191840.GA68514@logik.internal.network> <20090530162744.5d77e9d1@bhuda.mired.org> Date: Sat, 6 Jun 2009 13:16:32 -0700 Message-ID: From: Freddie Cash To: freebsd-hackers@freebsd.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: Request for opinions - gvinum or ccd? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 06 Jun 2009 20:16:34 -0000 On Sat, Jun 6, 2009 at 12:54 PM, Ivan Voras wrote: > Sorry to come into the discussion late, but I just want to confirm > something. > > The configuration below is a stripe of four components, each of which is > RAIDZ2, right? > > If, as was discussed later in the thread, RAIDZ(2) is more similar to > RAID3 than RAID5 for random performance, the given configuration can be > (very roughly, in the non-sequential access case) expected to deliver > performance of four drives in a RAID0 array? According to all the Sun documentation, the I/O throughput of a raidz configuration is equal to that of a single drive. Hence their recommendation to not use more than 8 or 9 drives in a single raidz vdev, and to use multiple raidz vdevs. As you add vdevs, the throughput increases. We made the mistake early on of creating a 24-drive raidz2 vdev. Performance was not very good. And when we had to replace a drive, it spent over a week trying to resilver. But the resilver operation has to touch every single drive in the raidz vdev. :( We remade the pool using 3x 8-drive raidz2 vdevs, and performance has been great (400 MBytes/s write, almost 3 GBytes/s sequential read, 800 MBytes/s random read). -- Freddie Cash fjwcash@gmail.com