Re: RAID 5 build time optimization question and experiments.

On Fri, Dec 11, 2009 at 8:57 AM, Cat'Killer [off-list ref] wrote:

quoted

On Fri Dec 11, 2009 at 02:55:31PM +0000, Cat'Killer wrote:

quoted

I found a way using Doug Gilbert's great sg3utils to zero all these
disks in a very efficient manner, using sgp_dd, at near drive
bandwidth, and proceeded to zero all the disks fully in about 4 hours!

Once done, I then created a RAID 5 on 10 disks, waited for the rebuild
to complete, stopped the array using mdadm, and dumped each of the
RAID's components superblocks to files.

<-snip->

quoted

The create worked fine and I waited for the rebuild to be complete
before stopping the array and dumping the SBs.

I then proceeded to write these same superblocks to 10 new similar
disks in a different system.

You could just do the create with --assume-clean, which should take very
little time at all.  If the drives were zeroed initially then this will
give you valid parity data.

Thank you for this, that's exactly what I was looking for. I had
looked in the manpage beforehand but I did not search for the right
terms nor assumed this would work in case of an array created ontop of
zeroed drives.

Thanks again.

Ben.

quoted

Cheers,
  Robin

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Yes, I had just come to a similar conclusion in a recent email series
and even provided a patch against the git copy of the manpage to
clarify the documentation.
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