Adding new raid partitions causes panic on reboot

[Andy Burns]

On 23/03/07, Jesse Keating <jkeating at redhat.com> wrote:

> Wild guess here, what if you repeat this scenario using parted instead of
> fdisk?

Booted from PXE and tried zeroing out the first few MB of /dev/sd[abcdef]2
still enough remnants of raid for kernel to allocate /dev/md0 to them
and panic with no root.

Rebooted again from PXE and deleted /dev/sd[abcdef]2 partitions,
system booted again (as expected)

Then re-created partitions with parted
mkpart primary ext2 4294MB 400GB
set 2 raid on
for each disk

Partitions visible without reboot, thank you :-)
What does parted do that fdisk and blockdev don't to allow live
partition changes?

something up with sizes though :-(

# sfdisk -l -uM /dev/sdc

Disk /dev/sdc: 48641 cylinders, 255 heads, 63 sectors/track
Units = mebibytes of 1048576 bytes, blocks of 1024 bytes, counting from 0

   Device Boot Start   End    MiB    #blocks   Id  System
/dev/sdc1   *     0+  4094-  4095-   4192933+  fd  Linux raid autodetect
/dev/sdc2      4094+ 381551- 377457- 386515867+  fd  Linux raid autodetect
/dev/sdc3         0      -      0          0    0  Empty
/dev/sdc4         0      -      0          0    0  Empty

each 2nd partition is 396MB, so array size should be under 1.8TB

yet mdadm thinks it's about to create a 3.5TB array,

 mdadm --create /dev/md1 --level=5 --chunk=256 --raid-devices=6
--spare-devices=0 --verbose /dev/sd[abcdef]2
mdadm: layout defaults to left-symmetric
mdadm: /dev/sda2 appears to be part of a raid array:
    level=raid5 devices=6 ctime=Tue Mar 20 23:09:36 2007
mdadm: /dev/sdb2 appears to be part of a raid array:
    level=raid5 devices=6 ctime=Tue Mar 20 23:09:36 2007
mdadm: /dev/sdc2 appears to be part of a raid array:
    level=raid5 devices=6 ctime=Tue Mar 20 23:09:36 2007
mdadm: /dev/sdd2 appears to be part of a raid array:
    level=raid5 devices=6 ctime=Tue Mar 20 23:09:36 2007
mdadm: /dev/sde2 appears to be part of a raid array:
    level=raid5 devices=6 ctime=Tue Mar 20 23:09:36 2007
mdadm: /dev/sdf2 appears to be part of a raid array:
    level=raid5 devices=6 ctime=Tue Mar 20 23:09:36 2007
mdadm: size set to 386515712K

Seems out by a factor of 2, some miscalculation of sectors and KB somewhere?

In my narrative above I'm playing a bit fast and loose with the terms
MB/MiB though I think parted an sfdisk use them correctly
respectively.