From owner-freebsd-hackers@FreeBSD.ORG Wed Jan 23 21:23:48 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id E024648C; Wed, 23 Jan 2013 21:23:48 +0000 (UTC) (envelope-from artemb@gmail.com) Received: from mail-vb0-f47.google.com (mail-vb0-f47.google.com [209.85.212.47]) by mx1.freebsd.org (Postfix) with ESMTP id 84C6BFCC; Wed, 23 Jan 2013 21:23:48 +0000 (UTC) Received: by mail-vb0-f47.google.com with SMTP id e21so1650535vbm.34 for ; Wed, 23 Jan 2013 13:23:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:x-received:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=24nHO+462d1riarIWZ5ktl944GDji+uBqmN8eJS75Cw=; b=wtDtseVtMbZ3aY9LCKhAvibga+3GBvllFcKrnr5X67xko9tcHej7CHS+5de55u6fPI mSw6UGC/vy7CCECS9XokyHrobwLanuG3gm1QUAbt5y5N6T47panY+5z88Plsbf9aYRwb BJ+8tcZyJOmfCWQiFx6pewFIAOURP7XVK3wOU5hUrF2n3gqhSZtAWoiOA/NF2vHRXjep XJTePdWwVJlP0KMPB9DQl+xJZ6xvPtA/W4SOFPS3uZFCcWQ3JUVtmSOXikZV/P2wK6Le vygIVFSomCJ6GD/z9Bp+NF/6F6yBB4QOUZnZn8/XbNuhvUyc2GIT26pdjqqP2LMPOjn+ X4hQ== MIME-Version: 1.0 X-Received: by 10.52.76.7 with SMTP id g7mr2694351vdw.95.1358976227679; Wed, 23 Jan 2013 13:23:47 -0800 (PST) Sender: artemb@gmail.com Received: by 10.220.123.2 with HTTP; Wed, 23 Jan 2013 13:23:47 -0800 (PST) In-Reply-To: References: <20130122073641.GH30633@server.rulingia.com> Date: Wed, 23 Jan 2013 13:23:47 -0800 X-Google-Sender-Auth: H1jEo4QrSn9xnvkNQGX15PeFTCk Message-ID: Subject: Re: ZFS regimen: scrub, scrub, scrub and scrub again. From: Artem Belevich To: Mark Felder Content-Type: text/plain; charset=ISO-8859-1 Cc: freebsd-fs , Wojciech Puchar , Chris Rees , FreeBSD Hackers X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Jan 2013 21:23:48 -0000 On Wed, Jan 23, 2013 at 1:09 PM, Mark Felder wrote: > On Wed, 23 Jan 2013 14:26:43 -0600, Chris Rees wrote: > >> >> So we have to take your word for it? >> Provide a link if you're going to make assertions, or they're no more than >> your own opinion. > > > I've heard this same thing -- every vdev == 1 drive in performance. I've > never seen any proof/papers on it though. "1 drive in performance" only applies to number of random i/o operations vdev can perform. You still get increased throughput. I.e. 5-drive RAIDZ will have 4x bandwidth of individual disks in vdev, but would deliver only as many IOPS as the slowest drive as record would have to be read back from N-1 or N-2 drived in vdev. It's the same for RAID5. IMHO for identical record/block size RAID5 has no advantage over RAID-Z for reads and does have disadvantage when it comes to small writes. Never mind lack of data integrity checks and other bells and whistles ZFS provides. --Artem