Hello,
On Fri, May 07, 2021 at 09:47:39AM +0800, d tbsky wrote:
> I thought someone test the performance of two ssd, raid-1 outperforms
> all the layout. so maybe under ssd it's not important?
If you're referring to this, which I wrote:
http://strugglers.net/~andy/blog/2019/06/01/why-linux-raid-10-sometimes-performs-worse-than-raid-1/
then it only matters when the devices have dramatically different
performance. In that case is was a SATA SSD and an NVMe, but
probably you could see the same with a rotational HDD and a SATA SSD.
Also, it was a bug (or rather a missing feature). RAID-10 was
missing the ability to choose to read from the least loaded device,
so it's the difference between getting 50% of your reads from the
much slower device compared to hardly any of them.
And Guoqing Jiang fixed it 2 years ago.
Cheers,
Andy
