Re: Changing Chunk Size on Array

[Neil Brown <neilb@suse.de>]

On Sat, 17 Jul 2010 16:15:55 -0500
"Leslie Rhorer" <lrhorer@satx.rr.com> wrote:

> 
> 	I'm thinking about changing the chunk size on one of my arrays in
> order to potentially improve performance.  The man page rather suggests -c
> is a vlaid option under Grow mode, although it doesn't specifically say
> mdadm supports it under --grow.  Is it indeed supported under mdadm 2.6.7.2
> and kernel 2.6.26-2?  Assuming so, I would like to know a bit more about the
> change before issuing the command.  Speficialy, what are the details of the
> process?  Does the entire (RAID 6) array have to be re-written, such as is
> the case with adding a drive to the array?  Does the recovery start
> immediately?  Can it be interrupted and then continue at a later time?

Yes, you can change chunksize with --grow.
I think you need mdadm-3.1.2 and kernel 2.6.32 though (version numbers might
not be accurate, but are close).

Yes, the entire array gets re-written just like adding an extra device.
The reshape does start immediately.
If you shutdown or crash, then on restart the reshape will pick up where it
left off.

NeilBrown