[CentOS] Growing RAID5 on CentOS 4.6

Ross S. W. Walker RWalker at medallion.com
Fri Aug 22 18:25:20 UTC 2008


Stephen Harris wrote:
> On Fri, Aug 22, 2008 at 08:41:25PM +0300, Jussi Hirvi wrote:
> > How about simply
> >     % mdadm --grow /dev/md3
> 
> % mdadm --grow  /dev/md3
> mdadm: no changes to --grow
> 
> > What do you get with
> >     % mdadm --detail /dev/md3
> 
> /dev/md3:
<snip>
>     Number   Major   Minor   RaidDevice State
>        0       8        1        0      active sync   /dev/sda1
>        1       8       18        1      active sync   /dev/sdb2
>        2       8       35        2      active sync   /dev/sdc3
>        3       8       52        3      active sync   /dev/sdd4
> 
>        4       8       65        -      spare   /dev/sde1

Stephen,

I don't think you can grow it without backing it up, destroying
it, rebuilding it with 5 devices, then restoring.

>From the man page:

       Grow   Grow  (or shrink) an array, or otherwise reshape it in some way.
              Currently supported growth options including changing the active
              size of component devices in RAID level 1/4/5/6 and changing the
              number of active devices in RAID1.

I take it to mean you can grow the segment size on all devices in the
array, say you swapped out 160GB drives with 320GB drives one by one
and now you want your array to fill up the remaining 160GB, then you
can grow it, but you can only add devices to a RAID1...

What do you think this is ZFS?

Sheesh!

-Ross

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