On 17/10/17 01:33, NeilBrown wrote:

On Mon, Oct 16 2017, Reindl Harald wrote:

quoted

Am 16.10.2017 um 15:54 schrieb Wols Lists:

quoted

Raid 10 is a complicated subject what with near and far, and whether it
will grow, etc etc.

I'm planning to raid-10 my swap partition, and while it doesn't matter
in the slightest because destroying and recreating will be no hassle for
swap, I'd like to understand what's going on.

If I remember correctly, there was a thread a little while back on
growing a raid-10? And you can't (for certain values of "can't" :-) do it?

Where's the best place to find info about near, far and offset layouts?

http://xmodulo.com/setup-raid10-linux.html

This patch has some good stuff, but

   Chunk Size, as per the Linux RAID wiki, is the smallest unit of data
   that can be written to the devices

I wonder where the Linux RAID wiki say that.  It is wrong.
The smallest unit of data that can be written to the devices is the
block size, which is hardware dependant and typically 512bytes or 4K.
This is not the same as the chunk size.

https://raid.wiki.kernel.org/index.php/RAID_setup#Chunk_sizes

I understand what it's saying - this is the smallest size passed down to 
the disk, not the smallest size that the disk can write ... :-)

This page has made it into the archaeology section so I don't plan to 
update it. And in context, it's reasonably clear what it means.

Cheers,
Wol