From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: SAS v SATA interface performance Date: Sat, 01 Dec 2007 15:01:40 -0500 Message-ID: <4751BDA4.9080102@rtr.ca> References: <47506237.3000406@clear.net.nz> <47507F9A.3080109@msgid.tls.msk.ru> <20071130231705.51e056f4@the-village.bc.nu> <475110A8.5090709@clear.net.nz> <87f94c370712010637o5efa9c4rd9a86ec5a3cba6ff@mail.gmail.com> <4751B3DA.6030508@clear.net.nz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from rtr.ca ([76.10.145.34]:3948 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751464AbXLAUBm (ORCPT ); Sat, 1 Dec 2007 15:01:42 -0500 In-Reply-To: <4751B3DA.6030508@clear.net.nz> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Richard Scobie Cc: linux-ide@vger.kernel.org Richard Scobie wrote: > > > Greg Freemyer wrote: > >> Also, if you have Port Multiplexers (PMPs) in use, that would be >> interesting to know. I don't even know if PMPs are supported via SAS >> controllers in 2.6.24 or not. ie. PMP support is new to 2.6.24 and >> only a few Sata controllers will have PMP support in 2.6.24. > > No, port multipliers are not in use here, the technology that SAS uses > is called port expansion. While I do not know much about the low level > operational differences, from a performance perspective, this is my > understanding. > > Port multiplication only permits one drive to be accessed at once, > whereas port expansion allows multiple drives to be accessed > simultaneously. .. SATA port multipliers (think, "hub") permit multiple drives to be active simultaneously. -ml