I have Replicated Gluster Storage which is used by Auto scaling Servers. Both, Auto scaling and Storage are allocated in two Availability zones.

Gluster:

Number of Bricks: 4 x 2 = 8
Transport-type: tcp
Bricks:
Brick1: gluster01:/storage/1a # Zone A
Brick2: gluster02:/storage/1b # Zone B
Brick3: gluster03:/storage/2a # Zone A
Brick4: gluster04:/storage/2b # Zone B
Brick5: gluster01:/storage/3a # Zone A
Brick6: gluster02:/storage/3b # Zone B
Brick7: gluster03:/storage/4a # Zone A
Brick8: gluster04:/storage/4b # Zone B

I used Round Robin DNS for Gluster entry point, so DNS name resolves to all of the storage server addresses which are returned in different order all the time:

# host storage.domain.com
storage.domain.com has address xx.xx.xx.x1
storage.domain.com has address xx.xx.xx.x2
storage.domain.com has address xx.xx.xx.x3
storage.domain.com has address xx.xx.xx.x4

The Storage is mounted with Native Gluster Client:

# grep storage /etc/fstab
storage.domain.com:/storage /storage glusterfs defaults,log-level=WARNING,log-file=/var/log/gluster.log 0 0

I have heard Gluster might be mounted with the first Server IP and after that it will fetch its configuration with the rest of Servers. Personally, I never tested single Server mount setup and I don't know how Gluster handles this.

On EC2, traffic among single Availability zone is free and between different zones is not. When Client in zone A writes to storage and IP of Storage in zone B is returned, it will cost me twice more for data transfer: Client (Zone A) -> Storage Server (Zone B) -> Replication to Storage Server (Zone A).

Question: Would it be better to mount Storage Server of the same zone, so that data transfer charges apply only for replication (A -> A -> B)?