From owner-freebsd-current@FreeBSD.ORG Tue Dec 15 15:01:54 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 696DB1065679; Tue, 15 Dec 2009 15:01:54 +0000 (UTC) (envelope-from mavbsd@gmail.com) Received: from mail-fx0-f227.google.com (mail-fx0-f227.google.com [209.85.220.227]) by mx1.freebsd.org (Postfix) with ESMTP id BC4B58FC15; Tue, 15 Dec 2009 15:01:52 +0000 (UTC) Received: by fxm27 with SMTP id 27so4276779fxm.3 for ; Tue, 15 Dec 2009 07:01:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:sender:message-id:date:from :user-agent:mime-version:to:cc:subject:references:in-reply-to :x-enigmail-version:content-type:content-transfer-encoding; bh=B9SSdLWFqt+o9Ex6VvPNyVW6iUQnGR1Lm0B7DRWrbhU=; b=mHbbBgfGSN73B1IBdtleBOTmy4Mg+fI06Ed+RsDdMZyjgntomRSO+6fYgymwohxATk JIiKL+qf5xmCY6alc4HRWKRQl7mQoDKI35z1Eu68HdlWBryq2UevPO1drT5OCAiaENzD E1DbvhHrDswMXMzLvsUsrrEwaF3abYOPqR94c= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; b=eJHTcJeVzF5BDDDOXhpMDa0Yv/8UFSkv0fzxBTDFlNaiDmOjqNd1LQlYvxkHE6u3xZ MpJTCjJ1cAhYwLb9OCQuYbrh/W7NeFKJwqPZ0JkCs+RPhqNVGDMj/iBfAuSXZ9YMOsCo ofrPRb+STER4etYuBtp/fm5n2VIyndvo3opmM= Received: by 10.223.14.140 with SMTP id g12mr1235445faa.50.1260889311944; Tue, 15 Dec 2009 07:01:51 -0800 (PST) Received: from mavbook.mavhome.dp.ua (pc.mavhome.dp.ua [212.86.226.226]) by mx.google.com with ESMTPS id 13sm1962814fxm.9.2009.12.15.07.01.50 (version=SSLv3 cipher=RC4-MD5); Tue, 15 Dec 2009 07:01:51 -0800 (PST) Sender: Alexander Motin Message-ID: <4B27A4DC.7070908@FreeBSD.org> Date: Tue, 15 Dec 2009 17:01:48 +0200 From: Alexander Motin User-Agent: Thunderbird 2.0.0.23 (X11/20091212) MIME-Version: 1.0 To: Wes Peters References: <20091119004651.7432a6e4.nork@FreeBSD.org> In-Reply-To: X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: freebsd-current@freebsd.org, Norikatsu Shigemura Subject: Re: How do I use NCQ of Intel X25-E(SSD) on ahci(4)? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Dec 2009 15:01:54 -0000 Wes Peters wrote: > On Wed, Nov 18, 2009 at 7:46 AM, Norikatsu Shigemura wrote: >> I have a Intel 64GB SSD(X25-E) and a Western Digital Caviar Green >> 1TB HDD (WD10EADS), and use them on ahci(4). ahci(4) can use NCQ >> of WD10EADS, but doesn't use NCQ of X25-E. > > How useful is NCQ on an SSD? Isn't the primary thrust of NCQ to allow > the disk to reorder writes to optimize the seek pattern? Many SSDs have several flash channels. Multiple parallel requests running allow controller to effectively use them in parallel. On my OCZ Vertex I am receiving about 30% speedup from using NCQ on many short read requests. If you look into Intel SSD's datasheet, you'll also see that all benchmarks are provided for maximal request queue. -- Alexander Motin