From owner-freebsd-stable@FreeBSD.ORG Tue Feb 16 20:24:22 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9AF64106566B for ; Tue, 16 Feb 2010 20:24:22 +0000 (UTC) (envelope-from fjwcash@gmail.com) Received: from mail-yx0-f172.google.com (mail-yx0-f172.google.com [209.85.210.172]) by mx1.freebsd.org (Postfix) with ESMTP id 56E848FC1D for ; Tue, 16 Feb 2010 20:24:22 +0000 (UTC) Received: by yxe2 with SMTP id 2so6633814yxe.7 for ; Tue, 16 Feb 2010 12:24:21 -0800 (PST) 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; bh=DJ5K2vdB9KmHREb913F1bcNf2gUfcS1N4hW8nGmiLzc=; b=yHVR8pHVlHNMhidCFUEb8RF4/iytiuXU1sj+AVCmBcXVyJEoOl/b7FWqI19a8B4iqF X2UnjcIcf9fJq6vJQvMYAm5tR/595ZaiFbLeJZeFjF24CROqKbkVD5ioHrkrx/JRYHEd jVVRlfwgK5vyvb4lk4kDHGneD7M57motyR37c= 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; b=P+lp7Wb7EkVga21J0qgG4mwRrRNEb9t162AE9loSqTF70jaLskoT+XIep4agq41X6V 0MVVdZ/Xb6U6BMM0fu2GT3ThksOzJlsfxLcM7rTQdTVItwWsMk3GSmsuwpQweE5NYd8H yPwpyf1evTgXNwmoJnKOPOkmNES4KDn1f+mx8= MIME-Version: 1.0 Received: by 10.231.144.66 with SMTP id y2mr2041078ibu.67.1266351861459; Tue, 16 Feb 2010 12:24:21 -0800 (PST) In-Reply-To: <20100216194707.GQ4648@cesium.hyperfine.info> References: <20100216194707.GQ4648@cesium.hyperfine.info> Date: Tue, 16 Feb 2010 12:24:21 -0800 Message-ID: From: Freddie Cash To: freebsd-stable@freebsd.org Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Subject: Re: raidz/2 stripe widths X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Feb 2010 20:24:22 -0000 On Tue, Feb 16, 2010 at 11:47 AM, Peter C. Lai wrote: > Which one might be "better" on pool that will consist of 6 disks: > > 6x raidz2 > or > 2 stripes of 3 disks in raidz? > > It should provide slightly less reliability (still allows for 2 disks to be > off the array at a time) but the latter should improve reads since a given > read only has to touch 3 spindles at a time instead of 5? > Depends. Do you want better reliability/redundancy (raidz2) or more throughput/IOPS (2x raidz1)? The max IOPS of a raidz vdev will be that of 1 disk. Thus, to get better IOPS, you have to have multiple raidz vdevs. The overly-simplistic way to look at is to think of the entire raidz vdev as a "single disk". Then it's an easy comparison: 1 disk is slower than 2 disks striped together. -- Freddie Cash fjwcash@gmail.com