From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Scobie Subject: Re: SAS v SATA interface performance Date: Sun, 02 Dec 2007 08:19:54 +1300 Message-ID: <4751B3DA.6030508@clear.net.nz> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.sauce.co.nz ([210.48.49.72]:50234 "EHLO smtp.sauce.co.nz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752594AbXLATVJ (ORCPT ); Sat, 1 Dec 2007 14:21:09 -0500 In-Reply-To: <87f94c370712010637o5efa9c4rd9a86ec5a3cba6ff@mail.gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org Cc: linux-ide@vger.kernel.org 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. Port expanders are selfcontained and do not require kernel support - the only kernel requirement, is support for the SAS HBA or RAID controller. See Xtore, Adaptec or Dell (MD1000), for suitable JBOD enclosures. Regards, Richard