How do I only use A records correctly, without changing nameservers?
I have a situation where, my domain is registered at dreamhost (DH), and nameservers are pointing to siteground (SG). And now I would like to move my hosting to Linode with minimum disruption.
I would like to continue using SG nameservers (due to emails), so my thinking is that I will setup A records for my domain to point to linode IP.
My question is then, how do I set this up on Linode? Documents I found mainly focus on changing the nameservers but this is not a viable option for me at the moment.
And I wish I had kept emails on DH and used A records for SG back then.
I don't know if above setup would cause any delays for the website load (added miliseconds due to nameserver routing etc.) - hope not?
If you wish to continue using Siteground's nameservers, you have to set the A record to point to your Linode instance from Siteground. You don't have to do anything DNS-related from Linode side.
On your issue about "additional routing", conceptually it takes the same number of steps to resolve to your domain. Dreamhost is just your registrar, Siteground will be your nameserver and Linode will host your app. Registrar is different from nameserver but most registrars also host nameservers for obvious reasons.