Hello Michal,

On Thu, 13 Nov 2008, Michal Soltys wrote:

quoted

is it possible to create md partitions larger than 0.4TB?

We have >=9TB RAID-0 systems, and I tried to create a partitionable 
two-partition md with mdadm --auto=mdp2 and partition it into for example 
16MB and ~9TB. For partitioning /dev/md_d0 I have tried sfdisk, fdisk, 
cfdisk, parted, ... Regardless of the partitioning tool, the ~9TB partition 
always ends up as 455780.07MB i.e. 0.4TB.

I'm assuming you tried standard MBR layout - you can't go above ~ 2TB limit 
with it - you need either GPT, or use the device directly (as in md0 case). I 
have one 1.5TB partition running happily on one of my systems (still within 
limits of old MBR layout, but under GPT).

Aha, with GPT it works perfectly,

   parted /dev/md_d0 --script mklabel gpt
   parted /dev/md_d0 --script mkpart primary1 0 128M
   yes | parted /dev/md_d0 -- mkpart primary2 128M -1
   ... mkfs.* ...
   parted /dev/md_d0 --script print
   Number  Start   End     Size    File system  Name      Flags
    1      17.4kB  128MB   128MB   ext2         primary1
    2      128MB   9252GB  9252GB  xfs          primary2

and the final size of md_d0p2 is a correct 9252GB. The system does not 
boot from RAID, we just use the raid0 for >>4 Gbps data acquisition. Good 
to know about the newer superblock versions (mdadm -e option).

Thanks for your help!

  - Jan