Andy Smith <andy@xxxxxxxxxxxxxx> > 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. sorry I didn't find that comprehensive report before. what I saw is that raid10 and raid1 performance are similar and raid1 is a little faster. so I just use raid1 at two disks conditions these years. like the discussion here https://www.reddit.com/r/homelab/comments/4pfonh/2_disk_ssd_raid_raid_1_or_10/ I don't know if the situation is the same now. I will try to do my testing. but I think in theory they are similar under multiple process.
