[ILUG] Booting a broken raid array

[Conor Wynne]

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Kenn Humborg wrote:
>> - partition as follows:
>>
>>   - /boot goes onto the compact flash card, set as the booting device
>> in the bios
>>   - create a slice of swap on each of the disks (say 500MB - 1GB each)
>> at the start of the disk
>>   - fill the rest of the disc with a software raid partition
>>   - repeat for additional disks
>>   - build desired raid level MD device on the partitions
>>   - put a single LVM volume on top of that (for future expansion)
> 
> If I read this right, your swap space is not on mirrored or
> raided storage.  So, when one disk fails, the system won't
> be able to swap data back in from that disk.  
> 
> While this shouldn't cause a kernel crash in Linux (since
> the kernel never swaps out its own data), it will crash
> any user-land process that needs to swap in from that swap 
> space.

it's like when the OOM killer invokes, avoid a panic by killing off
unimportant processes like your databases etc :-)

To me that's just as bad as a panic as your going to end up rebooting
either way.

> Your setup is protecting the data on the disks, but is not
> really giving you any higher availability.

Are we talking about a production environment or a home setup here?
I assume it's home, and in which case all I would bother RAIDing
anything other than the data. Even then I wouldn't bother wasting the
power. I would use an offline backup like a USBHDD jobby. Only switching
it on when required for a quick rsync, you'll find the disk lasts longer
that way too!

By all means, backup your /etc (it's generally tiny) and the data.
How long does it take to re-install and restore data? If it's for home
use, time is on your side. Production is a another matter.

> 
> Later,
> Kenn
> 
> 

Conor.

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