From owner-freebsd-hackers@FreeBSD.ORG Mon Nov 17 22:50:48 2014 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 501C9758 for ; Mon, 17 Nov 2014 22:50:48 +0000 (UTC) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "funkthat.com", Issuer "funkthat.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 0D23A2B9 for ; Mon, 17 Nov 2014 22:50:47 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id sAHMoiVk036915 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 17 Nov 2014 14:50:45 -0800 (PST) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id sAHMoiZV036914; Mon, 17 Nov 2014 14:50:44 -0800 (PST) (envelope-from jmg) Date: Mon, 17 Nov 2014 14:50:44 -0800 From: John-Mark Gurney To: Brandon Vincent Subject: Re: OT-ish SATA port replicators vs. SAS "expanders" Message-ID: <20141117225044.GS24601@funkthat.com> Mail-Followup-To: Brandon Vincent , FreeBSD Hackers References: <54693866.9040009@sentex.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Mon, 17 Nov 2014 14:50:45 -0800 (PST) Cc: FreeBSD Hackers X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 17 Nov 2014 22:50:48 -0000 Brandon Vincent wrote this message on Sun, Nov 16, 2014 at 17:26 -0700: > On Sun, Nov 16, 2014 at 4:51 PM, Mike Tancsa wrote: > > I don think a port multiplier is the same as a SAS expander and a SAS/SATA > > controller does not necessarily support port multipliers. > > You're absolutely correct. The SATA specifications if I recall > correctly, outline that providing support for port multipliers is > optional. Not to mention, the vast majority of chipsets that do have > support for port multipliers only provide the slower command-based > switching method [1], The LSI SAS 2008 chipset is not what you > typically find on the cheap consumer "fake RAID" cards which most > people have [2]. > > Most people who purchase this card are purchasing it for SAS, true > RAID, performance, and reliability. Thus, LSI is only going to provide > support for the far superior SAS expander technology. If you go w/ SATA PMs, make sure you get a controller that supports FIS-base switching instead of command based switching... You'll get much better performance w/ NCQ support... As for if the LSI SAS 2008 will support FBS, probably not, as it'll require the driver and/or firmware to be aware of how to handle things... This page has a list which includes if the controller supports FIS/FBS: https://ata.wiki.kernel.org/index.php/SATA_hardware_features It doesn't list the Marvell 88SE9235 that I'm using (but not w/ PMs), but Marvell's site says it does, and it uses the ahci driver, which means it should if you have a new enough version of FreeBSD that supports PMs... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."