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Re: raw io and lvm

To: "Matt D. Robinson" <yakker@xxxxxxxxxxxxxx>
Subject: Re: raw io and lvm
From: Chaitanya Tumuluri <chait@xxxxxxxxxxxxxxxxxxxx>
Date: Wed, 31 May 2000 12:12:33 -0700
Cc: "Kipp A. Aldrich" <kippa@xxxxxxx>, rawio@xxxxxxxxxxx
In-reply-to: Your message of "Tue, 30 May 2000 14:27:02 PDT." <Pine.LNX.4.21.0005301425500.31631-100000@xxxxxxxxxxxxxxxxxxx>
Sender: owner-rawio@xxxxxxxxxxx
Sorry for the delayed reponse; I was fighting INS battles 
over the weekend and early part of this week. :^)

I used the "raw" program from Stephen Tweedie's website which
is essentially the RH utility that Matt pointed you at in his
email. 

I have not looked into lvm based devices in this effort yet (or
`md' ones for that matter). That is on my todo list. Offhand, I'd 
suspect that this rawio patch will not work with lvm devices since
these are expecting buffer-head based requests....I'll have to 
get a dialogue going with Andrea Arcangeli/Martin Peters and a 
couple of LVM folks to see what can be done. It'd be good if they
do pitch in...

Cheers,
-Chait.

On Tue, 30 May 2000 14:27:02 PDT, "Matt D. Robinson" <yakker@xxxxxxxxxxxxxx> 
wrote:
>That sound about right, although I'm not entirely familiar
>with LVM to tell you a good answer.
>
>Can you use the 'dd.raw' to DD into and out of the device,
>so that you know your raw I/O is working?
>
>If so, then it's an LVM issue ... otherwise, it could still
>be a raw I/O configuration issue.  Hope this helps ...
>
>--Matt
>
>On Tue, 30 May 2000, Kipp A. Aldrich wrote:
>|>
>|>> 
>|>> There should be a 'raw' application available with RH 6.2 which
>|>> will bind the raw device to some block device.
>|>> 
>|>> What you'd want is:
>|>> 
>|>>         mknod /dev/raw c 162 0
>|>>         mknod /dev/raw2 c 162 2
>|>> 
>|>> Then you'd run:
>|>> 
>|>>         raw /dev/raw2 /dev/sdb4
>|>> 
>|>> (or something to that effect).
>|>> 
>|>> You can get the latest raw.c from the util-linux RPM off of freshmeat.net.
>|>> If you still have problems finding it, send a mail here.
>|>> 
>|>> --Matt
>|>
>|>Did that. Now if I try to use LVM's pvcreate on /dev/raw2 I get:
>|>"pvcreate -- invalid physical volume name "/dev/raw2""
>|>
>|>Guess it is not possible to use raw devices in LVM.
>|>
>|>Am I missing something here?  
>|>
>|>Thanks.
>|>
>|>kipp
>|>-- 
>|>Kipp A. Aldrich 
>|>Digital Video Engineering
>|>Industrial Light & Magic
>|>kippa@xxxxxxx 415.448.2443
>|>


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