Node cloning

Nordwall, Douglas J Nordwall at pnl.gov
Fri Apr 6 10:29:11 EDT 2001


Perhaps I am misinformed here...but doesn't repartitioning and reformatting a
disk find those bad blocks? Systemimager does a wipe of the disk locally, then
performs an rsync to move oer the files.

> -----Original Message-----
> From: Josip Loncaric [mailto:josip at icase.edu]
> Sent: Friday, April 06, 2001 7:11 AM
> Cc: beowulf at beowulf.org
> Subject: Re: Node cloning
> 
> 
> "Robert G. Brown" wrote:
> > 
> > > On Thu, 5 Apr 2001, Oscar Roberto [iso-8859-1] López 
> Bonilla wrote:
> > >
> > > > And then use the command (this will take long, so you 
> can do it overnight)
> > > >          cp /dev/hda /dev/hdb ; cp /dev/hda /dev/hdc ; 
> cp /dev/hda /dev/hdd
> > 
> > [...]  This approach to cloning
> > makes me shudder -- things like the devices in /dev 
> generally have to
> > built, not copied, there are issues with the boot blocks 
> and bad block
> > lists and the bad blocks themselves on both target and host.  raw
> > devices are dangerous things to use as if they were flatfiles.
> 
> I agree.  Whatever the protections built into today's drives, 
> there are
> still plenty of bad blocks that Linux needs to map out, and the
> information about them is stored in the filesystem.  This 
> disk dependent
> information must be built, not copied.
> 
> BTW, we found that about 10% of our IDE hard drives (mostly early
> Seagate 7200rpm UDMA models) had either too many bad blocks or bad
> blocks in unacceptable locations (like the swap partition) 
> and had to be
> replaced.  We now use a combination of Seagate and IBM 
> drives, and over
> the past two years about 20% of them have developed at least some bad
> blocks that we had to map out using the 'e2fsck -c ...' command.  
> 
> I read somewhere that the overall PC industry average fraction of disk
> drive problems is 17%.  This is quite significant, and if you are more
> careful about your disks than an average PC user, chances are that
> you'll find that 20-30% of the drives have some kind of problem. 
> Unfortunately, some cloning approaches (e.g. systemimager) do not
> include the 'badblocks' program to check the new disk *before*
> installation (although the check can be done after installation, this
> could be too late). 
> 
> Maintaining 1TB's worth of local disks on a cluster of 
> machines requires
> regular monitoring.  We check for problems monthly and fix them as
> needed.  
> 
> Sincerely,
> Josip
>  
> -- 
> Dr. Josip Loncaric, Research Fellow               
> mailto:josip at icase.edu
> ICASE, Mail Stop 132C           PGP key at 
> http://www.icase.edu./~josip/
> NASA Langley Research Center             
> mailto:j.loncaric at larc.nasa.gov
> Hampton, VA 23681-2199, USA    Tel. +1 757 864-2192  Fax +1 
> 757 864-6134
> 
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