Re: raw I/O support for Fedora Core 4

From: Arjan van de Ven
Date: Thu Mar 23 2006 - 05:04:43 EST


On Thu, 2006-03-23 at 14:54 +0530, 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 not getting compiled as it is obsolete in 2.6.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

the preferred interface is doing O_DIRECT io on the device node itself,
rather than going via a (slower) indirection layer such as "raw". ("raw"
is just a wrapper on top of O_DIRECT basically in 2.6 kernels so slower)

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