Re: How to use replacement?

[NeilBrown <neilb@suse.de>]

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On Mon, 4 Jun 2012 14:34:28 +0800 majianpeng <majianpeng@gmail.com> wrote:

> >On Mon, 4 Jun 2012 09:53:21 +0800 majianpeng <majianpeng@gmail.com> wrote:
> >
> >> Hi:
> >> 	At present, md is supporting replacement.
> >> 	In function: state_store()
> >> >   } else if (cmd_match(buf, "replacement")) {
> >> >		/* Can only set a device as a replacement when array has not
> >> >		 * yet been started.  Once running, replacement is automatic
> >> >		 * from spares, or by assigning 'slot'.
> >> >		 */
> >> 		I can using spare disk.But how to use slot?
> >
> >If you want to ensure that a particular device becomes a replacement for a
> >particular other device, then
> >  cd /sys/block/mdX/md
> >  echo frozen > sync_action
> >  echo NN:MM > new_dev  # where NN is major and MM is minor of new device
> 
> If the array had a persistent superblock, the operation returned error.
> The message like:
> [  262.934070] md: sde does not have a valid v1.2 superblock, not importing!
> How can do it ?
> 

You need to write a superblock out to the device first.
mdadm already does this when adding a spare to an array, and it is
a similar operation.

NeilBrown


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