Re: How to grow RAID1 mirror on top of LVM?

On Thursday March 13, aia21@cam.ac.uk wrote:

Is there a better way to do this?  I am hoping someone will tell me to  
use option blah to utility foo that will do this for me without having  
to break the mirror twice and resync each time.  (-;

Sorry, but no.  This mode of operation was never envisaged for md.
I would always put the md/raid1 devices below the LVM.

Every time you buy two drives, combine them into a RAID1, and add the
/dev/mdX as a PV for LVM.  Then grow you LVM devices whenever you
like.

If not, please consider this a feature request for mdadm.  (-:  It  
should have an option to detect that the underlying device has grown  
and thus write a new superblock  (or move the old one or whatever) at  
the end of the newly grown device instead of complaining that it does  
not exist.  Or something!  As it is, it is incredibly time consuming  
and inefficient.  )-:

I'll keep it in mind (Which it to say:  I will save this in my 'mdadm'
mailbox, and have a look through that mailbox next time I'm working on
improvements to mdadm).

NeilBrown