Your company runs a customer facing event registration site This site is built with a 3-tier architecture with web
and application tier servers and a MySQL database The application requires 6 web tier servers and 6
application tier servers for normal operation, but can run on a minimum of 65% server capacity and a single
MySQL database. When deploying this application in a region with three availability zones (AZs) which
architecture provides high availability?
A.
A web tier deployed across 2 AZs with 3 EC2 (Elastic Compute Cloud) instances in each AZ inside an Auto
Scaling Group behind an ELB (elastic load balancer), and an application tier deployed across 2 AZs with 3
EC2 instances in each AZ inside an Auto Scaling Group behind an ELB. and one RDS (Relational Database
Service) instance deployed with read replicas in the other AZ.
B.
A web tier deployed across 3 AZs with 2 EC2 (Elastic Compute Cloud) instances in each A2 inside an Auto
Scaling Group behind an ELB (elastic load balancer) and an application tier deployed across 3 AZs with 2
EC2 instances in each AZ inside an Auto Scaling Group behind an ELB and one RDS (Relational Database
Service) Instance deployed with read replicas in the two other AZs.
C.
d A web tier deployed across 2 AZs with 3 EC2 (Elastic Compute Cloud) instances in each AZ inside an
Auto Scaling Group behind an ELB (elastic load balancer) and an application tier deployed across 2 AZs
with 3 EC2 instances m each AZ inside an Auto Scaling Group behind an ELS and a Multi-AZ RDS
(Relational Database Service) deployment.
D.
A web tier deployed across 3 AZs with 2 EC2 (Elastic Compute Cloud) instances in each AZ Inside an Auto
Scaling Group behind an ELB (elastic load balancer). And an application tier deployed across 3 AZs with 2
EC2 instances In each AZ inside an Auto Scaling Group behind an ELB. And a Multi-AZ RDS (Relational
Database services) deployment.
Explanation:
http://highscalability.com/blog/2016/1/11/a-beginners-guide-to-scaling-to-11-million-users-on-amazons.html
https://www.airpair.com/aws/posts/building-a-scalable-web-app-on-amazon-web-services-p1
D
0
0
D is Correct bcos..in Question they have mentioned lastly they mentioned.
When deploying this application in a region with “three availability zones (AZs)”
which architecture provides high availability?
A- Wrong..bcos only 2 AZ`s
B- Here RDS is not high availability so partial availability of application tier
C- Wrongs..bcos only 2 AZ`s and our requirement is with “THREE AZ`s”
D- Right..bcos..first is 3 AZ`s condition is meet..AUTO SCALING for each AZs for 6 web tier servers and 6 application tier servers(2 for Each AZ`s)
and for DB “Multi-AZ RDS” (Relational Database services) it will give high
availability.
1
0
A is wrong because its RDS has read replica, needs Multi-AZ failover.
B is wrong for the same reason – needs Multi-AZ failover.
C is kind of OK, because 2 AZs DO provide HA for web and app and it has Multi-AZ RDS.
D is even better, but not good enough – minimal server load is 65%, which is 2/3 of 6 = 4 servers minimum to start with…
I guess we can rely on AutoScaling to bring it up to 4.. So D.
0
0
WE NEed 3 AZs with 2 instances each so because the application can work with 65% of the ressource capacity.
if we had 2 AZs with 3 instance, If an AZ fails, we are at 50% which is not sustainable, so A and C are out.
I choose D because Read replica does not improve availability, only performance
1
0