From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: SAS v SATA interface performance Date: Fri, 30 Nov 2007 22:06:31 -0500 Message-ID: <4750CFB7.7040400@rtr.ca> References: <4750A523.7010501@clear.net.nz> <20071201001740.7ffce6f6@the-village.bc.nu> 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]:1863 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757120AbXLADGc (ORCPT ); Fri, 30 Nov 2007 22:06:32 -0500 In-Reply-To: <20071201001740.7ffce6f6@the-village.bc.nu> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Alan Cox Cc: Richard Scobie , linux-ide@vger.kernel.org Alan Cox wrote: >> The comment I saw, which I'm trying to verify, mentioned the SATA drives >> "held the bus" or similar longer than SAS ones. > > SATA normally uses one link per device so the device side isn't contended > unless you descend into the murky world of port multipliers. .. And that's where NCQ comes into it's own, allowing full bus release so that other drives on the same port multiplier can burst as needed. I've only had a port multiplier here for a few days, and used only a pair of *notebook* SATA drives on it thus far. Both drives can stream at full rate without any slowdown -- that's 55MByte/sec from each drive, at the same time, for sequential reading, 100MByte/sec total. Notebook drives. Cheers