[Ocfs2-users] superblock backups, ASM vs OCFS2

[Jeremy Schneider]

Sunil and Saar - thanks for the quick replies!!

Quick follow-up question: would the 11g asmcmd "md_backup" command also be
able to quickly rebuild all of the disk header information without losing
any data?


On 12/13/07, Saar Maoz <Saar.Maoz at oracle.com> wrote:
>
>
> To avoid confusion, the paragraph I wrote is in context of ASM's
> management of superblock, not OCFS2.  OCFS2 was already responded to by
> Sunil in another reply.
>
> Regards,
>
> Saar.
>
> --
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>   ((  /\\  /\\ ||)  |\V/| /\\ /\\ >/ Consulting Software Engineer
>   _))//-\\//-\\||\  |||||//-\\\\//<_ Oracle Corporation
>   HQ: 650.50-mixOS  WK: 510.222.4224 Saar.Maoz at oracle.com  4op441
>   \\\\\\\\50-64967\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
>   ///Share your knowledge with others and compete with yourself///
>
>
> On Thu, 13 Dec 2007, Saar Maoz wrote:
>
> > Date: Thu, 13 Dec 2007 20:28:44 +0200 (Jerusalem Standard Time)
> > From: Saar Maoz <Saar.Maoz at oracle.com>
> > To: Jeremy Schneider <jeremy.schneider at ardentperf.com>
> > Cc: ocfs2-users at oss.oracle.com
> > Subject: Re: [Ocfs2-users] superblock backups, ASM vs OCFS2
> >
> > 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 at 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 at ardentperf.com>
> >> To: ocfs2-users at 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
> >>
> >>
> >
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-- 
Jeremy Schneider
Chicago, IL
http://www.ardentperf.com/category/technical
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