From owner-freebsd-questions@freebsd.org Thu Oct 15 21:09:09 2015 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id BD370A16158 for ; Thu, 15 Oct 2015 21:09:09 +0000 (UTC) (envelope-from wam@hiwaay.net) Received: from fly.hiwaay.net (fly.hiwaay.net [216.180.54.1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 83CD1100B for ; Thu, 15 Oct 2015 21:09:08 +0000 (UTC) (envelope-from wam@hiwaay.net) Received: from kabini1.local (dynamic-216-186-213-32.knology.net [216.186.213.32] (may be forged)) (authenticated bits=0) by fly.hiwaay.net (8.13.8/8.13.8/fly) with ESMTP id t9FL97pM003126 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO) for ; Thu, 15 Oct 2015 16:09:08 -0500 Subject: Re: Follow-up install questions References: <561F9FAC.9080308@hiwaay.net> <561FAEE7.2030505@hiwaay.net> <20151015161649.GA61524@neutralgood.org> Cc: FreeBSD Questions !!!! From: "William A. Mahaffey III" Message-ID: <562015F3.5020306@hiwaay.net> Date: Thu, 15 Oct 2015 16:14:37 -0453.75 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151015161649.GA61524@neutralgood.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Oct 2015 21:09:09 -0000 On 10/15/15 11:23, kpneal@pobox.com wrote: > On Thu, Oct 15, 2015 at 08:54:57AM -0453, William A. Mahaffey III wrote: >> On 10/15/15 08:40, Adam Vande More wrote: >>> On Thu, Oct 15, 2015 at 7:42 AM, William A. Mahaffey III >>> > wrote: >>> >>> Pursuant to ongoing issues trying to install FreeBSD 9.3R on my >>> Myth-TV box, I have some questions about provisioning another box, >>> also w/ 9.3R. That box is AMD A-10 APU based, w/ 8X 1 TB 2.5" >>> HDD's. Given the problems I am having getting the (smaller, >>> simpler box) going. I am pondering using ZFS on the larger box. To >>> that end, I have a couple of questions. ZFS supports (man page) >>> 'unmirrored pools'. Is that tantamount to striped RAID ? If so, >>> what sort of I/O performance can I look for there ? There was a >>> lengthy thread a few weeks ago on ZFS & performance. I (think I) >>> recall someone saying they used a bunch of 1-HDD vdevs to get some >>> semblance of good I/O performance w/ a RAIDZn configuration, is >>> that (additional layer of config) actually required ? My man page >>> says vdev's can be single devices or 'a collection of devices', >>> with devices being disks (individual HDD's ?), files, mirrors, or >>> raidz's. Are those mirrors necessarily ZFS mirrors, or can they be >>> gmirrors ? I am interested in maximizing the size of the storage >>> pool available, & the best I/O performance I can get. This box >>> will be backed up across the LAN onto other boxen, so I am >>> worrying less about HDD reliability & more about performance & max >>> available GiB's/TiB's. TIA & have a good one. > Don't mix ZFS with gmirror. If you are going to use mirrors then let > ZFS handle it. OK, roger that. > > ZFS stripes across vdevs. A vdev consisting of a single drive is allowed. > You can add and remove mirrors from a single drive vdev. There are _no_ > single drive RAIDZ* vdevs. > > A pool consisting of nothing but single-drive vdevs would indeed be an > "unmirrored pool". But if a single drive fails you lose the contents > of the entire pool. Roger that, that's why this box will be backed up across the LAN (daily rsync, weekly compressed tar), I'm good w/ the risk, I just want as many GiB's of storage & as much I/O performance as reasonably possible, & within the bounds of capability of the technology, which I don't always have a good grip on (viz my problems w/ the smaller MythTV box) :-/ .... > > As for performance, a RAIDZ* vdev will read and write at about the speed > of a single drive. A mirror vdev will write about the same speed unless > you have lots of drives in the mirror. In that case a mirror vdev's > writes will be slower the more drives you put in the mirror. But a mirror > vdev's _reads_ are supposed to scale with the number of drives in the > mirror. OK, roger that on the mirrored read, any idea about unmirrored reads/write ? I could imagine both scaling (possibly weakly, but scaling nonetheless) w/ # of drives, no ? > >>> Why is speed such a concern for you? A single SATA is easily enough >>> to read and write multiple 1080p streams concurrently. >>> >>> What do you have against white space? It's too painful to read further. >> & WTF about white space ? > Your writing does look like a wall of text. If you split it into multiple > paragraphs with no indenting and a blank line between them then it will > be much easier to make it to the end of one of your posts. Fair enough, I have heard for years that I write far too 'literarily', i.e. in prose, rather than technically .... I'll look into a 12-step ;-) .... -- William A. Mahaffey III ---------------------------------------------------------------------- "The M1 Garand is without doubt the finest implement of war ever devised by man." -- Gen. George S. Patton Jr.