From owner-freebsd-performance@FreeBSD.ORG Tue Apr 20 15:55:16 2004 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id A881C16A4CE for ; Tue, 20 Apr 2004 15:55:16 -0700 (PDT) Received: from gen129.n001.c02.escapebox.net (gen129.n001.c02.escapebox.net [213.73.91.129]) by mx1.FreeBSD.org (Postfix) with ESMTP id A4C7543D54 for ; Tue, 20 Apr 2004 15:55:15 -0700 (PDT) (envelope-from gemini@geminix.org) Message-ID: <4085AA4B.1020700@geminix.org> Date: Wed, 21 Apr 2004 00:55:07 +0200 From: Uwe Doering Organization: Private UNIX Site User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.6) Gecko/20040119 X-Accept-Language: en-us, en MIME-Version: 1.0 To: freebsd-performance@freebsd.org References: <20040420195010.GZ87362@nasby.net> <4085869E.7090306@he.iki.fi> In-Reply-To: <4085869E.7090306@he.iki.fi> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Received: from gemini by geminix.org with asmtp (TLSv1:AES256-SHA:256) (Exim 3.36 #1) id 1BG48z-000AIS-00; Wed, 21 Apr 2004 00:55:09 +0200 Subject: Re: vfs.hirunningspace on a 3ware 8506 X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Apr 2004 22:55:16 -0000 Petri Helenius wrote: > Jim C. Nasby wrote: > >> Has anyone done any testing to see what value of vfs.hirunningspace is >> optimal for a 3ware 8506-8? >> > Do the 3ware controllers actually care about this value due to the > onboard processing and cache? I thought all writes are satisfied > immediately? The controller itself doesn't care, but the kernel does. With the current implementation, the amount of memory associated with outstanding read requests is subtracted from vfs.hirunningspace. With many concurrent read requests there is no reserve left for write operations, so write performance can suffer substantially. This balancing effect is actually intended in order to give read requests some priority, but in high performance systems with fast, caching raid controllers the default value of said variable is too low and therefore poses a bottleneck. Uwe -- Uwe Doering | EscapeBox - Managed On-Demand UNIX Servers gemini@geminix.org | http://www.escapebox.net