Re: Raid5 to another raid level??

[NeilBrown <neilb@suse.de>]

On Fri, 2 Sep 2011 11:35:30 +0100 Michael Busby <michael.a.busby@gmail.com>
wrote:

> Great, will test that in a bit
> 
> will mdadm 3.2.2 support converting raid4 to raid5
> 
> "A RAID4 can change the number of devices or the size of individual
> devices. It cannot be converted to RAID5 yet (though that should be
> trivial to implement)"

I guess the man page needs updating.  You would need a reasonably recent
kernel... 2.6.30 or later.  I guess that isn't so recent any more.

NeilBrown


> 
> On 2 September 2011 11:22, NeilBrown <neilb@suse.de> wrote:
> > On Fri, 2 Sep 2011 10:12:32 +0100 Michael Busby <michael.a.busby@gmail.com>
> > wrote:
> >
> >> Thanks Neil
> >>
> >> Is there anyway back from raid0 to raid4 as i know once at raid0 i
> >> will no longer be able to add any disks, in theory i could change
> >> echo raid0 > /sys/block/md0/md/level,but this would require adding a
> >> missing disk to the raid4 at the same time, not sure how easy that
> >> would be todo
> >>
> >
> > Yes, you can switch from RAID0 to RAID4 in much the same way as you switch
> > from RAID4 to RAID0.
> > You can then freeze/add-disk/change-size/unfreeze/wait/switch-back-to-RAID0
> > to add more devices.
> >
> > mdadm-3.2.2 should be able to do all this for you.  i.e. you ask it to --grow
> > a RAID and --add some disks at the same time, and it will do all the required
> > magic.
> >
> > This hasn't been tested extensively, but should work in simple cases.
> >
> > Of course the more devices you have in a RAID0, the less reliability you have
> > - but e.g. as a cache for a tape backup system a large RAID0 is fine.
> >
> > NeilBrown
> >
> >
> >

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