From owner-freebsd-fs@freebsd.org Wed May 18 04:24:09 2016 Return-Path: Delivered-To: freebsd-fs@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 71B54B402DE for ; Wed, 18 May 2016 04:24:09 +0000 (UTC) (envelope-from lexa@lexa.ru) Received: from mx3.lexa.ru (ns503534.ip-198-27-68.net [198.27.68.102]) by mx1.freebsd.org (Postfix) with ESMTP id 53A8516EB for ; Wed, 18 May 2016 04:24:08 +0000 (UTC) (envelope-from lexa@lexa.ru) Received: by mx3.lexa.ru (Postfix, from userid 66) id 9733C224A5D; Wed, 18 May 2016 00:24:07 -0400 (EDT) Received: from [193.124.130.166] (unknown [193.124.130.166]) by home-gw.lexa.ru (Postfix) with ESMTP id A176D1801 for ; Wed, 18 May 2016 07:21:46 +0300 (MSK) Subject: Re: ZFS performance bottlenecks: CPU or RAM or anything else? To: "freebsd-fs@freebsd.org" References: <8441f4c0-f8d1-f540-b928-7ae60998ba8e@lexa.ru> <16e474da-6b20-2e51-9981-3c262eaff350@lexa.ru> <1e012e43-a49b-6923-3f0a-ee77a5c8fa70@lexa.ru> <86shxgsdzh.fsf@WorkBox.Home> From: Alex Tutubalin Message-ID: Date: Wed, 18 May 2016 07:21:46 +0300 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 May 2016 04:24:09 -0000 On 5/18/2016 12:11 AM, Steven Hartland wrote: > Raidz is limited essential limited to a single drive performance > per dev for read and write while mirror is single drive performance > for write its number of drives for read. Don't forget mirror is not > limited to two it can be three, four or more; so if you need more read > throughput you can add drives to the mirror. Do I understand it correctly: - single write of one large file (or singe local write to zvol shared via iSCSI) will be local: single or only several metaslabs - for RAIDZ each disk will get only part of throughput - for mirror, each disk included in write will receive full data size (and for single local write only limited number of disks to be included in write) If so, raidz will have huge write performance benefit in my case: single write of one large file. As for read speed, I hope to deal with it with large enough L2ARC on SSDs. > > To increase raidz performance you need to add more vdevs. While this > doesn't have to be double i.e. the same vdev config as the first it > generally a good idea. Again, multiple vdevs will help for multiple parallel writes, but not for single one? Alex Tutubalin