Re: ANNOUNCE: mdadm 1.6.0 - A tool for managing Soft RAID under Linux

On Friday June 4, robin@robinbowes.com wrote:

On Fri, June 4, 2004 7:29, Neil Brown said:

quoted

  - Further support for partitionable arrays included "--auto=" option
    and "auto=" config file entry which instructs mdadm to create the necessary
    device files after allocating an unused array number.

Neil,

I am interpreting this to mean that I can create, for example, a large (e.g. 1TB) RAID5
array and create smaller partitions (/home, /usr, etc) on top of the RAID5 array? Is
this correct?

Yes, this is correct.

Where can I read more about this?

Uhm.... Good question.  The are brief hints in
   man mdadm
and
   man mdadm.conf
but I guess I should put something in:
   man 4 md

In recent 2.6 kernels you can create partitionable md arrays.
The is no fixed major number.  The major number can be found by
looking for "mdp" in /proc/devices.
There are 64 minor numbers for each array, allowing up to 63
partitions. 

The simplest way to access this functionality is with

    mdadm --create /dev/md/XX --auto=partition --level= ....

to create, or
 
    mdadm --assemble /dev/md/XX --auto=partition .....

to assemble.  Alternately "auto=partition" can be put in mdadm.conf.

If you do this, it will create device files:
 
    /dev/md/XX   the whole array
    /dev/md/XX1  the first partition
    /dev/md/XX2  the second partition
    /dev/md/XX3  the third partition
    /dev/md/XX4  the fourth partition

More (or less) partitions can be created using e.g. --auto=partition8
to create 8 partition device files.

The arrays will appear in /proc/mdstat as

    md_dN

where N is the number that was chosen.

Then
   cfdisk /dev/md/XX

will allow you to partition the array.

I hope this helps.

NeilBrown

Thanks,

R.
-- 
http://robinbowes.com