From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phillip Susi Subject: Re: raw I/O support for Fedora Core 4 Date: Thu, 23 Mar 2006 10:47:34 -0500 Message-ID: <4422C316.5070305@cfl.rr.com> References: 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-kernel-owner@vger.kernel.org To: Yogesh Pahilwan Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org List-Id: linux-raid.ids The raw device driver is obsolete because it has been superseded by the O_DIRECT open flag. If you want to have dd perform unbuffered IO then pass the iflag=direct option for input, or oflag=direct option for output, and it will use O_DIRECT to bypass the buffer cache. This of course assumes that you mean "bypass the buffer cache" when you say "raw io". Yogesh Pahilwan wrote: > Hi All, > > I want to do raw I/O on MD RAID and LVM for fedora core 4(kernel 2.6.15.6). > > After doing googling I came to know that "raw" command does the raw > operation by linking > MD device and LVM volume to the raw device as > > # raw /dev/raw/raw1 /dev/md0. > > But when I search on this I came to know that there is no raw (/dev/rawctl) > device support available with 2.6 kernel. > I have also tried recompile the kernel sources with raw device support it is > not getting compiled as it is obsolete in 2.6. > If I want to include raw device support in my kernel what should I will have > to do, so that I > Will be able to do raw I/O on MD device and LVM volumes. > > Thanks and Regards, > Yogesh >