[ale] Grub and auxiliary boot partition

[Jeff Hubbs]

Jeff Lightner wrote:
> I can't imagine why anyone would prefer software RAID over hardware RAID
> (mirroring at least) on /boot.  
I didn't say I did.  I said I prefer not to rely on RAID [period] for /boot.
> For performance reasons alone it would
> be preferable 
I dunno - the 0.0378858 seconds it takes to read my kernel out of /boot 
is adequate.  Now, if it got to 0.04 seconds, I might really start to 
gripe. ;)
> and as posted by Greg it allows you to ignore dealing with
> grub because grub sees the RAID LUN not the individual disks.
>   
Non-issue.  /boot is basically a read-only entity to me; I don't even 
mount it unless it's to change kernels or modify grub.conf.

In this machine's case (8x2GHz Xeon cores), software RAID is faster.  
Furthermore, I've got one array that's a stripe set of seven mirror 
pairs that cross controllers, so I can actually lose a controller (as 
long as the failure mode doesn't trash the bus) and still have the array. 
> -----Original Message-----
> From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of Jeff
> Hubbs
> Sent: Thursday, April 30, 2009 10:23 PM
> To: Atlanta Linux Enthusiasts - Yes! We run Linux!
> Subject: Re: [ale] Grub and auxiliary boot partition
>
> Greg -
>
> I didn't mention the 24 additional disk drives and three 3Ware 8-drive 
> controllers because they weren't germane to my question. :) 
>
> I prefer not to rely on RAID for /boot. 
>
> - Jeff
>
> Greg Freemyer wrote:
>   
>> Jeff,
>>
>> I use a 2-disk 3ware controller specifically for my server boot
>>     
> drives.
>   
>> Seems like a 2-disk controller is about $100 and it prevents you
>> worrying about grub issues.
>>
>> Greg
>>
>> On Thu, Apr 30, 2009 at 11:21 AM, Jeff Hubbs <jeffrey.hubbs at gmail.com>
>>     
> wrote:
>   
>>   
>>     
>>> I have a server with two disks that I use for booting and rooting -
>>>       
> sda and
>   
>>> sdb.  I partition them like this:
>>>
>>> |--sda1=/boot-----|--sda2 (type fd)------------------------|
>>>
>>> |--sdb1=/auxboot--|--sdb2 (type fd)------------------------|
>>>
>>> sdb1 and sdb2 are made into md0 in kernel RAID 1 and md0 is mounted
>>>       
> as /.
>   
>>> sda1 and sdb1 have the bootable flag set.  /auxboot holds the same
>>>       
> files as
>   
>>> /boot.
>>>
>>> I want to have things such that if sda is dead, grub can be told to
>>>       
> boot
>   
>>> entirely using just sdb.
>>>
>>> When I install grub, I envision these commands:
>>>
>>> grub> root (hd0,0)
>>>
>>> grub> setup (hd0)
>>> grub> root (hd1,0)
>>> grub> setup (hd1)
>>>
>>>
>>> Does that look like it will do what I want, acknowledging that the
>>>       
> settings
>   
>>> in grub.conf in /boot
>>> would come up and therefore would have to be changed by hand in the
>>>       
> grub
>   
>>> start menu before actually
>>>
>>> booting?
>>>
>>> If so, I expect I could do away with the human intervention by
>>>       
> putting sda
>   
>>> and sdb in the BIOS'
>>> boot list in that order, changing the grub.conf in /auxboot to use
>>>       
> sdb2 as
>   
>>> /, and then running the
>>>
>>> grub commands above.
>>>
>>> What do you think?
>>>
>>> - Jeff
>>>
>>>
>>>
>>> _______________________________________________
>>> Ale mailing list
>>> Ale at ale.org
>>> http://mail.ale.org/mailman/listinfo/ale
>>>
>>>
>>>     
>>>       
>>
>>   
>>     
>
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