Basic Aws- interview Question
Basic Aws- interview Question
1)
How are Spot Instance, On-demand Instance, and
Reserved Instance different from one another?
Both Spot Instance and
On-demand Instance are models for pricing.
|
Spot Instance |
On-demand Instance |
|
With Spot Instance, customers can purchase compute capacity with no
upfront commitment at all. |
With On-demand Instance, users can launch instances at any time based
on the demand. |
|
Spot Instances are spare Amazon instances that you can bid for. |
On-demand Instances are suitable for high-availability needs of applications. |
|
When the bidding price exceeds the spot price, the instance is
automatically launched, and the spot price fluctuates based on supply and
demand for instances. |
On-demand Instances are launched by users only with the pay-as-you-go
model. |
|
When the bidding price is less than the spot price, the instance is
immediately taken away by Amazon. |
On-demand Instances will remain persistent without any automatic
termination from Amazon. |
|
Spot Instances are charged on an hourly basis. |
On-demand Instances are charged on a per-second basis |
I have some private servers on my premises, also I have distributed some
of my workload on the public cloud, what is this architecture called?
A) Virtual Private
Network
B) Private Cloud
C) Virtual Private
Cloud
D) Hybrid Cloud
Answer will be
Hybrid Cloud
Explanation: This type of architecture would be a hybrid cloud. Why?
Because we are using both, the public cloud, and your on premises servers i.e
the private cloud. To make this hybrid architecture easy to use, wouldn’t it be
better if your private and public cloud were all on the same
network(virtually). This is established by including your public cloud servers
in a virtual private cloud, and connecting this virtual cloud with your on
premise servers using a VPN(Virtual Private Network).
What does the following command do
with respect to the Amazon EC2 security groups?
ec2-create-group CreateSecurityGroup
A) Groups the user
created security groups into a new group for easy access
B) Creates a new
security group for use with your account.
C) Creates a new
group inside the security group.
D) Creates a new
rule inside the security group.
Answer
B.
Explanation: A Security group is just like a
firewall, it controls the traffic in and out of your instance. In AWS terms,
the inbound and outbound traffic. The command mentioned is pretty straight
forward, it says create security group, and does the same. Moving along, once
your security group is created, you can add different rules in it. For example,
you have an RDS instance, to access it, you have to add the public IP address
of the machine from which you want access the instance in its security
group.
3) You have a distributed application that periodically processes large
volumes of data across multiple Amazon EC2 Instances. The application is
designed to recover gracefully from Amazon EC2 instance failures. You are
required to accomplish this task in the most cost effective way.
Which of the following will meet your requirements?
A)
Spot
Instances
B)
Reserved
Instances
C)
Dedicated
Instances
D)
On
Demand Instances
Answer: A
Explanation: Since the work
we are addressing here is not continuous, a reserved instance shall be idle at
times, same goes with On Demand instances. Also it does not make sense to
launch an On Demand instance whenever work comes up, since it is expensive.
Hence Spot Instances will be the right fit because of their low rates and no
long term commitments.
4) How is stopping and terminating
an instance different from each other?
Starting, stopping and terminating are the three states in an
EC2 instance, let’s discuss them in detail:
Stopping
and Starting an instance: When an instance is stopped, the
instance performs a normal shutdown and then transitions to a stopped state.
All of its Amazon EBS volumes remain attached, and you can start the instance
again at a later time. You are not charged for additional instance hours while
the instance is in a stopped state.
Terminating an
instance: When an instance is terminated, the instance performs a normal
shutdown, then the attached Amazon EBS volumes are deleted unless the
volume’s deleteOnTermination attribute is set to false. The
instance itself is also deleted, and you can’t start the instance again at a
later time.
5) How will you access the data on EBS in AWS ?
Elastic block storage as the name indicates provides
persistent, highly avaialble and high performance block level storage that can
be attached to a running EC2 instance. The storage can formatted and mounted as
a file system or the raw storage can be accessed directly
6) What is the boot time for an
instance store backed instance ?
The boot time for an Amazon Instance Store -Backed AMI is usually
less than 5 minutes.
7) Is it possible to vertically scale on
an Amazon Instance? If yes, how ?
Following are the steps to scale an Amazon Instance vertically –
·
Spin up a larger Amazon instance than the existing one.
·
Pause the exisiting instance to remove the root ebs volume from the
server and discard.
·
Stop the live running instance and detach its root volume.
·
Make a note of the unique device ID and attach that root volume to the
new server.
·
Start the instance again.
7) What is the total number of buckets
that can be created in AWS by default ?
100 buckets can be
created in each of the AWS accounts. If additional buckets are required,
increase the bucket limit by submitting a service limit increase.
8) Is it possible to cast-off S3
with EC2 instances ? If yes, how ?
It is possible to cast-off S3
with EC2 instances using root approaches backed by native occurrence storage.
9) How will you configure an
instance with the application and its dependencies , and make it ready to serve
traffic?
You can acheive this with the
use of lifecycle hooks. They are powerful as they let you pause the
creation or termination of an instance so that you can sneak peak in and
perform custom actions like configuring the instance, downloading the required
files, and any other steps that are required to make the instance ready.Every
auto scaling group can have multiple lifecycle hooks.
10) What are the important features of
a classic load balancer in EC2 ?
·
The high availability feature ensures that the traffic is distributed
among EC2 instances in single or multiple availability zones.This ensures high
scale of availability for incoming traffic.
·
Classic load balancer can decide whether to route the traffic or not
based on the results of health check.
·
You can implement secure load balancing within a network by
creating security groups in a VPC.
·
Classic load balancer supports sticky sessions which ensure that the
traffic from a user is always routed to the same instance for a seamless
experience.
11) Will you use
encryption for S3 ?
It is better to consider
encryption for sensitive data on S3 as it is a proprietary technology.
12) How will you bind the user session
with a specific instance in ELB (Elastic Load Balancer) ?
This can be achieved by
enabling Sticky Session.
13) What are the possible connection
issues you encounter when connecting to an EC2 instance ?
·
Unprotected private key file
·
Server refused key
·
Connection timed out
·
No supported authentication method available
·
Host key not found,permission denied.
·
User key not recognized by the server, permission denied.
14) What is the difference between
Amazon S3 and EBS ?
|
|
EBS |
|
|
Paradigm |
Object Store |
Filesystem |
|
Security |
Private Key or Public Key |
Visible only to your EC2 |
|
Redundancy |
Across data centers |
Within the data center |
|
Performance |
Fast |
Superfast |
15) Can you run multiple
websites on an EC2 server using a single IP address?
More than one elastic IP is
required to run multiple websites on EC2.
16) What happens when you reboot an EC2 instance?
Rebooting an instance is just
similar to rebooting a PC. You do not return to image’s original state,
however, the contents of the hard disk are same as before the reboot.
17) What are the storage
class available in Amazon s3?
·
Amazon S3 standard
·
Amazon S3 standard-infrequent Access
·
Amazon S3 Reduced Redundancy Storage
·
Amazon Glacier
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