[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 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://oss.oracle.com/pipermail/ocfs2-users/attachments/20071213/1ad0c422/attachment.html
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 > ------------------------------------------------------------------------ > > _______________________________________________ > Ocfs2-users mailing list > Ocfs2-users@oss.oracle.com > http://oss.oracle.com/mailman/listinfo/ocfs2-users
Jermey, In 11.1.0.7 (and beyond) we will have a backup of the disk header (the first 4k). Prior to that, we have been able in most circumstances to reconstruct the disk header using KFED. KFED will still be the tool to restore the disk header going forward, it will just be a simpler, more reliable procedure. Regards, Saar. -- __ _ _ __ _ _ _ _ ___ _____________________________ (( /\\ /\\ ||) |\V/| /\\ /\\ >/ Consulting Software Engineer _))//-\\//-\\||\ |||||//-\\\\//<_ Oracle Corporation HQ: 650.50-mixOS WK: 510.222.4224 Saar.Maoz@oracle.com 4op441 \\\\\\\\50-64967\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ ///Share your knowledge with others and compete with yourself/// On Thu, 13 Dec 2007, Jeremy Schneider wrote:> Date: Thu, 13 Dec 2007 10:58:44 -0600 > From: Jeremy Schneider <jeremy.schneider@ardentperf.com> > To: ocfs2-users@oss.oracle.com > Subject: [Ocfs2-users] superblock backups, ASM vs OCFS2 > > [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 > > 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 > >-------------- next part -------------- _______________________________________________ Ocfs2-users mailing list Ocfs2-users@oss.oracle.com http://oss.oracle.com/mailman/listinfo/ocfs2-users