@asapkota @TheRavenKing Are yes! There is currently a couple of bugs that relate to your current experience.
creating a raid1pool makes a single pool but in your case raid10 is also ending up looking like a single. I have added your findings to this outstanding issue. In the issue there is a work around for the time being though.
But unfortunately to see the state of the pool and to apply the workaround I believe you may also run into recently opened #issue752.
So not looking that smooth for you right now I’m afraid.
Also, and you may not like this, Raid levels above 1 are still not generally mature in btrfs at the moment, there are a couple of informative discussions on this matter in this forum over at:-
http://forum.rockstor.com/t/question-about-raid5-6-stability/56
and another concerning raid levels beyond 5/6 in btrfs:-
http://forum.rockstor.com/t/btrfs-raid-parity-beyond-raid5-6/154
@TheRavenKing apparently it is possible for btrfs to create raid1 for example on drives of dissimilar size, there is going to be wastage though but interesting to know that it can; see this github #issue509 for some background on this.
But all these matters have now been highlighted so hopefully things will be a little smoother / more functional very soon.