@shankarsingh , Please confirm whether this is a Stretched cluster or not - if it is then there *should* be 2 Fault Domains (each with 3 data-nodes) configured + Witness.
If this is the case then you cannot use RAID5 as a Storage Policy on either single site as each only has 3 nodes for component placement whereas RAID5 requires 4 nodes - by 'No preference' do you mean a policy that isn't pinned to one site? If so then that is basically going to be RAID5 across sites which would likely have poor performance and is very likely not what you want here.