DNS Clustering questions

1. first dnsonly (hostname ns1.domain.tld with nameservers ns1.domain.tld, ns2.domain.tld)
- i add dns cluster for second dnsonly and select standalone
(but got this: "The reverse trust relationship does not currently work without an access hash file on the remote server. You must login to the remote server and add this server to its cluster manager manually if you want the other server to be able to access this one." i used api tokens, is this problem? i must use public kay?)

DNS Path Diagram

ns1.domain.tld


2. second dnsonly (hostname ns2.domain.tld with nameservers ns1.domain.tld,ns2.domain.tld)
- a add dns cluster for first dnsonly and select standalone
(but got this: "The reverse trust relationship does not currently work without an access hash file on the remote server. You must login to the remote server and add this server to its cluster manager manually if you want the other server to be able to access this one." i used api tokens, is this problem? i must use public kay?)

DNS Path Diagram
ns1.domain.tld

setup webserver whm, hostname s1.domain.tld with nameservers ns1.domain.tld,ns2.domain.tld
- i add dns cluster for first and second dnsonly and select sync


DNS Path Diagram

s1.domain.tld

• ↳ ns2.domain.tld
• ↳ ns1.domain.tld

(like cPanel "guid dns cluster configuration docs" #direct links)


after i create account and point that domain to nameservers ns1 and ns2 everything work ok


is this correct setup?
dnsonly need to be standalone and webserveras set to sync to that dns only clusters?

second question when i add account on webserver dns records are written to webserver and dns clusters right?
if is that correct how i can backup dns cluster servers? what if dnsonly server fail(hdd...) do i need backup for dnsonly? what is on it?

also i setup second server and tried to add domain which is added already to server1 and i got error that dns exists so i think this is all setup ok right?