On Wed, 9 Dec 2009 19:34:04 -0800
Michael Evans [off-list ref] wrote:

On Wed, Dec 9, 2009 at 5:43 PM, Neil Brown [off-list ref] wrote:

quoted

On Wed, 9 Dec 2009 19:29:04 +0800
hank peng [off-list ref] wrote:

quoted

I think it is better to implement this function in kernel's md layer.
I wonder what Neil Brown think of this?

I don't think it is worth the effort.
You probably would save some CPU time as you don't need to XOR, but as has
been said, we are usually IO bound, not CPU bound.

With the current arrangement, you can start using the array immediately - you
don't have to wait for the initial recovery to complete.
If you zeroed all devices at create time, you would have to wait for that to
complete before using the array.

So I see very little gain, and significant cost.

NeilBrown

When I assemble an array I tend to have checked the devices before
hand; it would not be difficult to make the final pass a zeroing pass
if I knew I could vastly speed up post-assembly performance.  As I
stated, it's merely a lack of clarity in the documentation.

If you would like to create a patch against the man page, I would be happy to
accept it.

NeilBrown