Re: /proc/mdstat showing a device missing from array

[evoltech@2inches.com]

Quoting Neil Brown <neilb@suse.de>:

> On Sunday May 13, evoltech@2inches.com wrote:
> > 
> > 
> > Hello all,
> > 
> > I just set up a new raid 5 array of 4 750G disks and am having a strange
> > experience where /proc/mdstat is showing that one device is missing from
> the
> > array.  The output from a "--detail" shows that there is some unnamed
> device
> > that has been removed from the array and I don't understand why or how to
> fix
> > it.  Can someone please shed some light?
> 
> A raid5 is always created with one missing device and one spare.  This
> is because recovery onto a spare is faster than resync of a brand new
> array.

This is unclear to me.  Do you mean that is how mdadm implements raid5 creation
 or do you mean that is how raid5 is designed?  I havn't read about this in any
raid5 documentation or mdadm documentation.  Can you point me in the right
direction?

> 
> The real problem here is that recovery has not started.
> If you 
>   mdadm -S /dev/md2
>   mdadm -A /dev/md2 /dev/sd[def]
>   mdadm /dev/md2 -a /dev/sdg
> it will start recovery.
> 
> This bug was fixed in mdadm-2.5.2

The recovery of the array has started, thanks!

Sincerely,
Dennison Williams