Message-ID: <49AE3BF6.2010600@turknet.net.tr>
Date: Wed, 04 Mar 2009 10:29:42 +0200
From: Tarkan Erimer <tarkan.erimer@turknet.net.tr>
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To: David Newall <davidn@davidnewall.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: Failover Kernel
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On 03/03/2009 05:29 AM, David Newall wrote:
> It sounds like you want everything to just continue running.  I don't
>    
Yes, exactly. Backup kernel will take control when a crush occured 
without need a reboot or halt.
> see how that can be done.  All of those in-kernel tables and structures
> would need to be migrated, and it follows, because there was a crash,
> that any of them might have been corrupted.  Worse, you want this to
> save you when you try running a new kernel which crashes, and being a
> new kernel, it follows that any of those structures could be different;
> it might not be possible to create equivalent structures for different
> kernel versions.
>
>    
Yes, that's right and it's the first thing needed to overcome. Maybe, it 
could be implemented like this :

- Primary kernel could be 2.6.x or 2.6.x.y (2.6.28 or 2.6.28.1)
- Backup kernel could be one of these .y fix releases only: Like 2.6.28.5

So; when they're from the same version, it will prevent kernel API and 
structure changes.
For resuming by backup kernel: The primary kernel could write a journal 
about the needed things for backup to resume. Like process IDs, memory 
and process situations etc. The same manner as the Journalled File 
Systems did (they write a journal what they did to recover/resume at 
crash/disaster time).

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