On Wed, 9 Dec 2009 15:30:02 +0000
Robin Hill [off-list ref] wrote:

On Wed Dec 09, 2009 at 08:31:54PM +0530, senthilkumar.muthukalai@wipro.com wrote:

quoted

Hi,

I am trying to add a disk to a Linear Raid which was created with 2
disks.
We use linux-2.6.18 and mdadm-2.6.4.
I guess these support the above mentioned disk addition.

Why do you guess this?  The manual page should tell you exactly what's
supported, and even mdadm 3.1.1 makes no mention of support for growing
linear RAID:

        Currently supported growth options including changing the active
        size of component devices and  changing  the  number  of active
        devices  in RAID levels 1/4/5/6, changing the RAID level between
        1, 5, and 6, changing the chunk size and layout  for RAID5  and
        RAID5, as well as adding or removing a write-intent bitmap

Hmm... guess I should update that documentation, shouldn't I .....

Adding a device to a linear is supported since 2.6.18.

NeilBrown