From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andreas Enge <andreas@enge.fr>
Subject: Re: [PATCH} Add RAID devices.
Date: Sun, 31 Jul 2016 10:52:03 +0200
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To: myglc2 <myglc2@gmail.com>
Cc: guix-devel@gnu.org

On Sat, Jul 30, 2016 at 07:05:25PM -0400, myglc2 wrote:
> > I might write a more detailed blog post about this; there is a little
> > subtlety with the non-automatic determination of dependencies between
> > devices, so one needs to make sure that the partitions to be assembled
> > are present before the mdadm command is executed.
> I rebooted and the array is not assembled ;-(

Strange! But I will also tell you the subtlety ;-)  Here is a trick to use
(thanks to Ludovic):
(define md0
  (mapped-device
    (source (list "/dev/sda2" "/dev/sdb2"))
      (target "/dev/md0")
      (type raid-device-mapping)))
(operating-system
...
  (mapped-devices (list md0))
  (file-systems (cons (file-system
                        (title 'device)
                        (device "/dev/md0")
                        (dependencies (list md0))
                        (mount-point "/")
                        (type "ext4"))
                      %base-file-systems))

The "dependencies" field makes sure that the file system is only mounted
after the array is assembled; I am not sure that this is your problem,
but you might want to give it a try.

In the long run, this should be reprogrammed: Devices and file systems
should wait until all their "inputs" are present, or at least wait for
a reasonable time.


Andreas