Re: about raid5 recovery when created

[Robin Hill <robin@robinhill.me.uk>]

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On Tue Dec 08, 2009 at 09:01:23PM +0800, hank peng wrote:

> Hi, all:
> As we know, when a raid5 array is created, recovery will be going on
> which involves some read, one xor and one write. Since there is no
> real data in the disk at the time, besides, if I am willing to wait
> for recovery to complete and then use this raid5, how about adding
> support for a fast recovery method? Right now, what is in my mind is
> zero all disks which belong to this raid5. I think it will increase
> raid5 recovery speed when created and decrease CPU usage, since all
> zero is also XORed.
> What do raid developers think?
> 
It'll decrease CPU usage but increase I/O - you're now needing to write
to all disks.  Most systems will be I/O limited rather than CPU limited,
so the current approach works better.  If you want to zero the disks
then do this before creating the array - you can then use --assume-clean
to skip the resync process.

Cheers,
    Robin
-- 
     ___        
    ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |

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