From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: About seting up Raid5 on a four disk box. Date: Wed, 14 Oct 2009 17:08:58 -0400 Message-ID: <4AD63DEA.8090906@tmr.com> References: <70ed7c3e0910130704l1f1f7f0ar66271d85295c667b@mail.gmail.com> <70ed7c3e0910130810r58ab391id2fbfdff6200dcd8@mail.gmail.com> <70ed7c3e0910132340q1c4acdfbxa6938261088acca3@mail.gmail.com> <70ed7c3e0910140641x74c12a75k6f00df2ed3cbade0@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: ap23563m@gmx.com Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Antonio Perez wrote: > Majed B. wrote: > > >> Your applications can request as much files as they want regardless of >> their location, but the mechanical heads move together, so they can be >> at a single location at a point of time reading a single stream of a >> file (or multiple files if they were next to each other on the >> physical platter). >> > > Yes that's completely correct, and it's the job of the "elevator" (*) on the > "md" code to decide which sector, and in what order, such sectors will be > serviced. If the "elevator" is aware of the underlying hardware, it will do > the right thing if there are several md or just one. > > The elevator is part of disk access, not md. It schedules head motion for all users of the drive. > *(I am not an expert on this, is just what I got from Robin) > > -- Bill Davidsen Unintended results are the well-earned reward for incompetence.