[Ocfs2-users] superblock backups, ASM vs OCFS2

[Sunil Mushran]

http://oss.oracle.com/projects/ocfs2-tools/news/article_2.html
Backup superblock has been available with ocfs2-tools 1.2.3 (Mar 2007).

More info can be found in the faq:
http://oss.oracle.com/projects/ocfs2/dist/documentation/ocfs2_faq.html#BACKUPSB

Jeremy Schneider wrote:
> [Also posted to Oracle-L]
>
> Just wondering, does anyone know much about "superblock" backups in 
> ASM vs OCFS2?
>
> I ran into an interesting case a month or so back where someone had 
> accidentally tried to initialize their ASM disks with linux LVM...  
> and written the LVM headers to the disk.  It was just a few bytes at 
> the very top of the disk - but it was enough to totally hose ASM.  
> Which started me thinking, "if this was a filesystem then I'd have a 
> backup superblock that I could recover".  Who knows - maybe ASM has a 
> backup of its header block - but it's all proprietary and if there's a 
> tool that will recover an ASM header then it's probably buried at 
> Oracle support somewhere.
>
> Looks like OCFS2 includes superblock backups since this patchset:
> http://lkml.org/lkml/2007/1/22/148 <http://lkml.org/lkml/2007/1/22/148>
>
> Not sure if ckfs will recover them but since it's open source it'd be 
> trivial to put together a utility that would recover a superblock.
>
> This seems to me to be a great reason to choose OCFS2 over ASM.  
> Recovering a backup superblock is MUCH faster than recreating the 
> entire volume and restoring data from backup!!!  I don't even know if 
> you could use dd to try to backup your ASM disk headers - since it's 
> proprietary I don't know what's in those blocks.
>
> Anyone have any thoughts on this?  Is there anything I'm missing here?
>
> Jeremy
>
>
> -- 
> Jeremy Schneider
> Chicago, IL
> http://www.ardentperf.com/category/technical
> ------------------------------------------------------------------------
>
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