From owner-freebsd-questions@FreeBSD.ORG Tue Aug 10 12:46:36 2010 Return-Path: Delivered-To: freebsd-questions@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C427A1065670 for ; Tue, 10 Aug 2010 12:46:36 +0000 (UTC) (envelope-from bf1783@googlemail.com) Received: from mail-ww0-f50.google.com (mail-ww0-f50.google.com [74.125.82.50]) by mx1.freebsd.org (Postfix) with ESMTP id 5E4BA8FC12 for ; Tue, 10 Aug 2010 12:46:35 +0000 (UTC) Received: by wwb13 with SMTP id 13so1231847wwb.31 for ; Tue, 10 Aug 2010 05:46:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:received:reply-to:date :message-id:subject:from:to:cc:content-type; bh=BfGB0vJzeIIFXYZ0LQNGXwLk4zDlltQz22EHuc/29pk=; b=XVD+wikP0gw5ldjygS8p/R5estx25kGouXWSVZEZ1jibilHu1fdBJJGRFoX6Glq435 YPbOmOACnYifoKmoa0EyZV8wDz/lreg33bvsXlHO4HahQgcVZ9aRF0GnW0ZyANvFd+n3 rcTYfYZHhXhFCenlsWji06+2lM4gPIpdpqK5k= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:reply-to:date:message-id:subject:from:to:cc :content-type; b=wVqcgLvpa2H4yMTWf9q75Ms0SwPppRRl8GdHk2yxHGW3o0uP0eAhn/+//KRsA721eD G6SRW2TVo+ain47HGC/Nj4B+9Z7nLPHGDfbjKmDOV6PI4G4jiBwusVEVd0ujUr1llp1S eQhKvdMyWJu62JQsV9EAt2M5m006XPR9ZXYJs= MIME-Version: 1.0 Received: by 10.216.54.132 with SMTP id i4mr3855866wec.50.1281444395264; Tue, 10 Aug 2010 05:46:35 -0700 (PDT) Received: by 10.216.183.212 with HTTP; Tue, 10 Aug 2010 05:46:15 -0700 (PDT) Date: Tue, 10 Aug 2010 12:46:15 +0000 Message-ID: From: "b. f." To: freebsd-questions@FreeBSD.org Content-Type: text/plain; charset=ISO-8859-1 Cc: Dick Hoogendijk Subject: Re: AHCI driver X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: bf1783@gmail.com List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Aug 2010 12:46:36 -0000 >Is it really better to enable AHCI driver? Almost certainly, yes. If your BIOS and SATA controller use AHCI, and are recognized by the ahci(4), mvs(4), or siis(4) drivers (I think that these drivers are built as kernel modules by default in the recent versions of FreeBSD, and don't require the use of a custom kernel with the non-default ATA_CAM option -- all you have to do is load them at boot time, either manually or via loader.conf(5)), then you will be able to use features like NCQ and better power management with disk drives that support those features. This can give you substantial benefits. If your BIOS and/or SATA controller don't support AHCI, in order to use cam(4) you must build a custom kernel with the ATA_CAM option. In that case you may still see some benefits, but they won't be as dramatic as in the AHCI case. If I recall correctly, the only disadvantage to this option is that it prevents the use of ataraid(4) -- everything else has a (usually slightly better) counterpart with the option, and it is only a matter of configuring your system to use it and learning how to use the new management tools (like camcontrol(8)), rather than the old tools (like atacontrol(8)). And yes, if you use the new drivers or the ATA_CAM option, some of your disks will probably show up as /dev/adaX, rather than the old /dev/adX. So make sure that you adjust fstab(5) and device.hints(5) as necessary before rebooting. b.