Dirk Jagdmann wrote:

Hello experts,

I have a raid1 array with two drives working. It /dev/md0 built from
/dev/hda and /dev/hdb. Now I'd like to split it into two array with
one drive each (and then later add spares to my two arrays again). I
know that I can remove one drive from the array with: mdadm /dev/md0
-f /dev/hdb -r /dev/hdb , however I'm not sure what the superblock of
/dev/hdb now contains and how I could use the contents of /dev/hdb as
the starting point for my new /dev/md1 array? I did not find anything
in the manpage of mdadm which would provide me an automatic split.

So what are your advises?

The fast way (not redundant):
  You can mark hdb as failed, then remove it. Then you can create a new 
array using hdb and a missing device.

The safe way:
  get your additional drives, call then hdc and hdd just for discussion.
 add hdc to the existing array and let it rebuild, then mark hdb as 
failed and remove. Create a new array from hdb and hdd.

I'm sure someone will tell me if I left out a step.

-- 
bill davidsen [off-list ref]
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979