From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: NCQ general question Date: Wed, 01 Mar 2006 08:49:10 -0500 Message-ID: <4405A656.1030602@rtr.ca> References: <5d96567b0602282304o558fb564jd72784bafdd289f5@mail.gmail.com> <440561CB.30201@yahoo.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <440561CB.30201@yahoo.de> Sender: linux-raid-owner@vger.kernel.org To: Gentoopower Cc: "Raz Ben-Jehuda(caro)" , Linux RAID Mailing List , "linux-ide@vger.kernel.org" List-Id: linux-ide@vger.kernel.org Gentoopower wrote: > Raz Ben-Jehuda(caro) wrote: >> i am thinking of buying a promise card sataII pcix. >> they have two types, a card which support NCQ >> and another that does not. >> What is the bennifit of buying a card with NCQ tagging ? >> > How about: http://en.wikipedia.org/wiki/Native_command_queueing Yuck.. what a lousy wiki entry. NCQ vs. TCQ: NCQ has a much more efficient low-level protocol, making the host-side (controller, operating-system) quite a bit simpler than with NCQ. Both use 32-deep queue depths, and neither of them are worth a damn on Linux yet. Except possibly in the libata ahci driver, or vendor-provided drivers (open source, even) for some chipsets. In theory, NCQ/TCQ can speed up a very busy fileserver that is handling mostly tiny I/O requests. Practically no measurable benefit for single-user systems. Cheers