Re: ext3 journal on software raid (was Re: PROBLEM: Kernel 2.6.10 crashing repeatedly and hard)

[Brad Campbell <brad@wasp.net.au>]

Alvin Oga wrote:
> 
> hi ya brad
> 
> On Wed, 5 Jan 2005, Brad Campbell wrote:
> 
> 
>>Alvin Oga wrote:
>>
>>>	for swap ... i personally don't see any reason to mirror
>>>	swap partitions ...
>>>		- once the system dies, ( power off ), all temp
>>>		data is useless unless one continues from a coredump 
>>>		( from the same state as when it went down initially )
>>
>>I beg to differ on this one. Having spend several weeks tracking down random processes dying on a 
>>machine that turned out to be a bad sector in the swap partition, I have had great results by 
>>running swap on a RAID-1. If you develop a bad sector in a non-mirrored swap, bad things happen 
>>indeterminately and can be a royal PITA to chase down. It's just a little extra piece of mind.
> 
> 
> okay .... if the parts of disks is bad that is used for swap, 
> mirroring might help ... 
> 
> but, i wonder, how/why the system used that portion of swap in the first
> place
> 	- even for raid, if sector-10 in swap is bad, why would raid keep
> 	trying to write there instead of to sector-1000

Picture lpd gets swapped out on a friday night. Over the weekend it is not used and the drive 
develops a bad sector in the middle of the file. Monday morning I want to print and the system tries 
to page lpd back in again. *boom*.

I have not looked at the system swap algorithms, but I doubt they include automatic bad block 
management and read after write verification. I'm making big assumptions here, but I'm assuming they 
rely on a bad block table created by mkswap and an otherwise clean, functioning swap area.

Regards,
Brad