Re: RAIDframe changes its unit number

[Greg Oster <oster%netbsd.org@localhost>]

On Wed, 30 Sep 2015 15:11:35 +0200
Frank Wille <frank%phoenix.owl.de@localhost> wrote:

> Hi,
> 
> these days I have set up a Synology DS209j with a RAID-1 kernelized
> RAIDframe, using the components /dev/wd0a and /dev/wd1a.
> 
> All worked well, so I started to test some failure scenarios.
> 
> Disconnecting wd0 was fine and the system boots from wd1a with
> "component0 failed".
> 
> Then I replaced wd0 with another disk, which previously also has been
> auto-configured as /dev/raid0 during some tests, but is otherwise
> completely different. Now the system started with /dev/raid0
> and /dev/raid1, where both showed a failed component.
> 
> Ok, I realized my error and zeroed wd0's MBR and disklabel. But after
> a reboot my RAIDframe was still auto-configured as /dev/raid1,
> although raid0 no longer existed! Even disconnecting wd0 didn't
> change that.

RAIDframe tries really hard to remember what it was last configured
as... 

> And, even worse, when I connect my original wd0a component again I get
> raid0 with wd0a and failed component1, and raid1 with wd1a and failed
> component0.
> 
> Is it possible to change the "Last configured as..." setting on wd1
> back to raid0? Or do I have to reconstruct wd1 from wd0 now?

Not easily.  You can play around with nuking disklabels and stuff to
eventually get things right, and use 'raidctl -C' to re-configure, but
all of that is probably more effort than it's really worth.

> And wouldn't it be nice to fix RAIDframe, so that a
> previous /dev/raid1 is automatically configured as /dev/raid0 again,
> when raid0 does not exist in the system? Or doesn't that make sense
> for some reason?

Imagine a system where /dev/raid0a is /, /dev/raid1e is /tmp,
and /dev/raid2e is /bigdatabase.  Further, suppose that raid1 'goes
away', and that now /dev/raid2e is magically configured as /dev/raid1e.
What happens on boot when /tmp is cleared, given that /etc/fstab hasn't
changed to reflect the new location of /bigdatabase?

I agree that it'd be nice to have an IOCTL for raidctl to change which
device a RAID set will show up as on next reboot... It's not that hard
to do -- just requires time to do a little coding.  

Later...

Greg Oster