On 2019/7/26 上午2:37, David Sterba wrote:
> On Thu, Jul 18, 2019 at 02:27:49PM +0800, Qu Wenruo wrote:
>> RAID10 can accept as much as half of its disks to be missing, as long as
>> each sub stripe still has a good mirror.
> 
> Can you please make a test case for that?

Fstests one or btrfs-progs one?

> 
> I think the number of devices that can be lost can be higher than a half
> in some extreme cases: one device has copies of all stripes, 2nd copy
> can be scattered randomly on the other devices, but that's highly
> unlikely to happen.
> 
> On average it's same as raid1, but the more exact check can potentially
> utilize the stripe layout.
> 
That will be at extent level, to me it's an internal level violation,
far from what we want to improve.

So not that worthy.

Thanks,
Qu