From owner-freebsd-fs@freebsd.org Tue May 17 21:35:58 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 A3D43B3FBEA for ; Tue, 17 May 2016 21:35:58 +0000 (UTC) (envelope-from fullermd@over-yonder.net) Received: from mail.infocus-llc.com (mail.infocus-llc.com [199.15.120.13]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 8249F125C for ; Tue, 17 May 2016 21:35:58 +0000 (UTC) (envelope-from fullermd@over-yonder.net) Received: from draco.over-yonder.net (c-75-65-60-66.hsd1.ms.comcast.net [75.65.60.66]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.tarragon.infocus-llc.com (Postfix) with ESMTPSA id 3r8Vxf4z8LzX2; Tue, 17 May 2016 16:35:50 -0500 (CDT) Received: by draco.over-yonder.net (Postfix, from userid 100) id 3r8Vxd6xw5z1mp; Tue, 17 May 2016 16:35:49 -0500 (CDT) Date: Tue, 17 May 2016 16:35:49 -0500 From: "Matthew D. Fuller" To: Freddie Cash Cc: Steven Hartland , "freebsd-fs@freebsd.org" Subject: Re: ZFS performance bottlenecks: CPU or RAM or anything else? Message-ID: <20160517213549.GK24656@over-yonder.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Editor: vi X-OS: FreeBSD X-Virus-Scanned: clamav-milter 0.99 at mail.tarragon.infocus-llc.com X-Virus-Status: Clean User-Agent: Mutt/1.6.0-fullermd.4 (2016-04-01) 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: Tue, 17 May 2016 21:35:58 -0000 On Tue, May 17, 2016 at 02:16:16PM -0700 I heard the voice of Freddie Cash, and lo! it spake thus: > > They're not asking for ways to improve the performance of a > raidz-based pool; they're asking why they get different performance > metrics from the exact same pool when they change the CPU and RAM. More specifically, as I read it, different performance in a very specific metric; single-thread linear bulk writes. That doesn't seem like it would benefit heavily from a lot of cores available, or from RAM bandwidth or size above a pretty low threshold. Of course, it's not just changing the CPU and RAM; it's also the motherboard, and possibly the HBA (at least the bus the HBA is on, if it's a card being transplanted with the pool). And the Core 2 would be back in the plain-old FSB era, so RAM access would be competing with the disk IO on the bus. -- Matthew Fuller (MF4839) | fullermd@over-yonder.net Systems/Network Administrator | http://www.over-yonder.net/~fullermd/ On the Internet, nobody can hear you scream.