Installer doesn't seem to allow partitioning of /dev/mdX
I am raising this here for discussion as to whether this is intentional
behaviour or not.
I am installing Debian Wheezy on a system with two 1TB hard drives,
configured in the BIOS as a RAID1 pair and a single volume, "Volume0".
This motherboard uses IMSM metadata.
Thanks to http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=684708 this
is now detected correctly using mdadm instead of dmraid:
* /dev/md127 (also /dev/md/imsm0) is the container
* /dev/md126 (also /dev/md/Volume0) is the data
and md126 starts resyncing immediately.
However the installer does not let me partition this. It shows:
RAID1 device #126 - 950.2 GB Software RAID device
#1 950.2GB
512.0 B unusable
I can select #1, I can nominate what kind of filesystem it is (or "do
not use"), I can wipe it with random data, but I cannot delete #1 nor
create a partition within it.
What I wanted was to create:
/dev/md126p1 - for /boot filesystem
/dev/md126p2 - for alternate /boot filesystem (e.g. installing future
version of Linux)
/dev/md126p3 - for LVM
I know from previous experience that md volumes can be partitioned in
this way, but the installer doesn't appear to let me.
Workaround: go back into the BIOS and create distinct volumes within the
IMSM container.
This should be fine for my usage case, but if instead of using IMSM I
had wanted to create a simple /dev/md127 using native metadata, and then
partition it, I think I would be stuck.
Workaround 2: you can partition drives and then mirror the partitions as
different /dev/mdX devices. But this means when you come to swap a
drive, you cannot simply replace the failed drive: you must first
prepare the new one by manually partitioning it in the same way as its
partner, and then you must re-add the mirror pairs individually.
Has this been discussed before? Is partitioning of md devices
intentionally blocked in the installer?
Thanks,
Brian Candler.
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