[Also posted to <span class="gmail_quote">Oracle-L]<br><br></span>Just wondering, does anyone know much about "superblock" backups in ASM vs OCFS2?<br><br>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.
<br><br>Looks like OCFS2 includes superblock backups since this patchset:<br><a href="http://lkml.org/lkml/2007/1/22/148" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">http://lkml.org/lkml/2007/1/22/148
</a><br><br>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.
<br><br>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.
<br clear="all"><br>Anyone have any thoughts on this? Is there anything I'm missing here?<br><br>Jeremy<br><span class="sg"></span><br><br>-- <br>Jeremy Schneider<br>Chicago, IL<br><a href="http://www.ardentperf.com/category/technical">
http://www.ardentperf.com/category/technical</a><br>