Add a couple of AWS questions and exercises

EBS & ELB mainly.

README.md

@@ -10,7 +10,7 @@
 
 :busts_in_silhouette:  Join our [DevOps community](https://www.facebook.com/groups/538897960007080) where we have discussions and share resources on DevOps
 
-:pencil:  You can add more questions and exercises by submitting pull requests :) Read about contribution guidelines [here](CONTRIBUTING.md)
+:pencil:  You can add more exercises by submitting pull requests :) Read about contribution guidelines [here](CONTRIBUTING.md)
 
 ****
 
@@ -7605,7 +7605,7 @@ A load balancer accepts (or denies) incoming network traffic from a client, and
 </b></details>
 
 <details>
-<summary>What benefits load balancers provide?</summary><br><b>
+<summary>Why to used a load balancer?</summary><br><b>
 
 * Scalability - using a load balancer, you can possibly add more servers in the backend to handle more requests/traffic from the clients, as opposed to using one server.
 * Redundancy - if one server in the backend dies, the load balancer will keep forwarding the traffic/requests to the second server so users won't even notice one of the servers in the backend is down.
@@ -8276,6 +8276,12 @@ With vertical scaling alone, the component still remains a single point of failu
 In addition, it has hardware limit where if you don't have more resources, you might not be able to scale vertically.
 </b></details>
 
+<details>
+<summary>Which type of cloud services usually support vertical scaling?</summary><br><b>
+
+Databases, cache. It's common mostly for non-distributed systems.
+</b></details>
+
 <details>
 <summary>Explain Horizontal Scaling</summary><br><b>
 
@@ -8283,7 +8289,7 @@ Horizontal Scaling is the process of adding more resources that will be able han
 </b></details>
 
 <details>
-<summary>What is the disadvange of Horizontal Scaling? What is often required in order to perform Horizontal Scaling?</summary><br><b>
+<summary>What is the disadvantage of Horizontal Scaling? What is often required in order to perform Horizontal Scaling?</summary><br><b>
 
 A load balancer. You can add more resources, but if you would like them to be part of the process, you have to serve them the requests/responses.
 Also, data inconsistency is a concern with horizontal scaling.

exercises/aws/README.md

@@ -29,6 +29,14 @@ Note: Provided solutions are using the AWS console. It's recommended you'll use
 | Volume Creation | EC2, EBS | [Exercise](ebs_volume_creation.md) | [Solution](solutions/ebs_volume_creation.md) | Easy |
 | Snapshots | EC2, EBS | [Exercise](snapshots.md) | [Solution](solutions/snapshots.md) | Easy |
 | Create an AMI | EC2, AMI | [Exercise](create_ami.md) | [Solution](solutions/create_ami.md) | Easy |
+| Create EFS | EC2, EFS | [Exercise](create_efs.md) | [Solution](solutions/create_efs.md) | Easy |
+
+#### AWS - ELB
+
+|Name|Topic|Objective & Instructions|Solution|Comments|
+|--------|--------|------|----|----|
+| Application Load Balancer | ELB, ALB | [Exercise](app_load_balancer.md) | [Solution](solutions/app_load_balancer.md) | Easy |
+| Multiple Target Groups | ELB, ALB | [Exercise](alb_multiple_target_groups.md) | [Solution](solutions/alb_multiple_target_groups.md) | Easy |
 
 #### AWS - Lambda
 
@@ -341,10 +349,10 @@ Storage Optimized:
 EBS
 </b></details>
 
-##### AWS EC2 - Storage
+##### AWS EC2 - EBS
 
 <details>
-<summary>Explain what is Amazon EBS</summary><br><b>
+<summary>Explain Amazon EBS</summary><br><b>
 
 [AWS Docs](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AmazonEBS.html): "provides block level storage volumes for use with EC2 instances. EBS volumes behave like raw, unformatted block devices."
 </b></details>
@@ -393,12 +401,6 @@ Yes, with multi-attach it's possible to attach a single EBS volume to multiple i
 True
 </b></details>
 
-<details>
-<summary>How to move EBS volumes between availability zones?</summary><br><b>
-
-Using snapshots.
-</b></details>
-
 <details>
 <summary>What EBS volume types are there?</summary><br><b>
 
@@ -438,6 +440,14 @@ HDD - sc1
 SSD: gp2, gp3, io1, io2
 </b></details>
 
+<details>
+<summary>True or False? In EBS gp2 volume type, IP will increase if the disk size increases</summary><br><b>
+
+True.
+</b></details>
+
+##### AWS EC2 - Instance Store
+
 <details>
 <summary>If you would like to have an hardware disk attached to your EC2 instead of a network one (EBS). What would you use?</summary><br><b>
 
@@ -494,15 +504,33 @@ False. EFS scales automatically and you pay-per-use.
 </b></details>
 
 <details>
-<summary>Which EFS mode would you use if need maximum throughput?</summary><br><b>
+<summary>What EFS modes are there?</summary><br><b>
 
-Performance Mode (Max I/O): This provides high throughput and it's used for big data, media processing, etc.
+* Performance mode
+  * General purpose: used mainly for CMS, web serving, ... as it's optimal for latency sensitive applications
+  * Max I/O: great for scaling to high levels of throughput and I/O operations per second
+* Throughput mode
+  * Bursting: scale throughput based on FS size
+  * Provisioned: fixed throughput
+</b></details>
+
+<details>
+<summary>Which EFS mode would you use if you need to perform media processing?</summary><br><b>
+
+Performance Mode (Max I/O): It provides high throughput and scales to operations per second. Mainly used for big data, media processing, etc.
 </b></details>
 
 <details>
 <summary>What is the default EFS mode?</summary><br><b>
 
-Performance Mode (General Purpose): Used for web servers, CMS, etc.
+Performance Mode (General Purpose): Used for web serving, CMS, ... anything that is sensitive to latency.
+</b></details>
+
+<details>
+<summary>What EFS storage tiers are there?</summary><br><b>
+
+* Standard: frequently accessed files
+* Infrequent access: lower prices to store files but it also costs to retrieve them
 </b></details>
 
 ##### AWS EC2 - Pricing Models
@@ -825,7 +853,7 @@ Amazon definition: "AWS Fargate is a serverless compute engine for containers th
 Learn more [here](https://aws.amazon.com/fargate)
 </b></details>
 
-#### AWS Storage
+#### AWS - S3
 
 <details>
 <summary>Explain what is AWS S3?</summary><br><b>
@@ -910,7 +938,6 @@ Storage classes offered today:
     * have 9x9% durability
 
 More on storage classes [here](https://aws.amazon.com/s3/storage-classes)
-
 </b></details>
 
 <details>
@@ -988,14 +1015,6 @@ Learn more [here](https://docs.aws.amazon.com/AmazonS3/latest/dev/transfer-accel
 <summary>What storage options are there for EC2 Instances?</summary><br><b>
 </b></details>
 
-<details>
-<summary>What is AWS Snowmobile?</summary><br><b>
-
-"AWS Snowmobile is an Exabyte-scale data transfer service used to move extremely large amounts of data to AWS."
-
-Learn more [here](https://aws.amazon.com/snowmobile)
-</b></details>
-
 #### AWS Disaster Recovery
 
 <details>
@@ -1056,23 +1075,92 @@ True
 A transport solution which was designed for transferring large amounts of data (petabyte-scale) into and out the AWS cloud.
 </b></details>
 
-##### AWS ELB
+#### AWS - ELB
 
 <details>
 <summary>What is ELB (Elastic Load Balancing)?</summary><br><b>
 
-AWS definition: "Elastic Load Balancing automatically distributes incoming application traffic across multiple targets, such as Amazon EC2 instances, containers, IP addresses, and Lambda functions."
+[AWS Docs](https://aws.amazon.com/elasticloadbalancing): "Elastic Load Balancing automatically distributes incoming application traffic across multiple targets, such as Amazon EC2 instances, containers, IP addresses, and Lambda functions."
+</b></details>
 
-More on ELB [here](https://aws.amazon.com/elasticloadbalancing)
+<details>
+<summary>True or False? Elastic Load Balancer is a managed resource (= AWS takes care of it)</summary><br><b>
+
+True. AWS responsible for making sure ELB is operational and takes care of lifecycle operations like upgrades, maintenance and high availability.
+</b></details>
+
+<details>
+<summary>What types of AWS load balancers are there?</summary><br><b>
+
+* Classic Load Balancer (CLB): Mainly for TCP (layer 4) and HTTP, HTTPS (layer 7)
+* Application Load Balancer (ALB): Mainly for HTTP, HTTPS and WebSocket
+* Network Load Balancer (NLB): Mainly for TCP, TLS and UDP
+* Gateway Load Balancer (GWLB): Mainly for layer 3 operations (IP protocol)
+</b></details>
+
+<details>
+<summary>Which load balancer would you use for services which use HTTP or HTTPS traffic?</summary><br><b>
+
+Application Load Balancer (ALB).
+</b></details>
+
+<details>
+<summary>True or False? With ALB (Application Load Balancer) it's possible to do routing based on query string and/or headers</summary><br><b>
+
+True.
+</b></details>
+
+<details>
+<summary>Explain "health checks" in the context of AWS ELB</summary><br><b>
+
+Health checks used by ELB to check whether EC2 instance(s) are properly working.<br>
+If health checks fail, ELB knows to not forward traffic to that specific EC2 instance where the health checks failed.
+</b></details>
+
+<details>
+<summary>True or False? AWS ELB health checks are done on a port and a route</summary><br><b>
+
+True.
+
+For example, port `2017` and endpoint `/health`.
 </b></details>
 
 <details>
 <summary>What types of load balancers are supported in EC2 and what are they used for?</summary><br><b>
 
-  * Application LB - layer 7 traffic
+* Application LB - layer 7 traffic<br>
-  * Network LB - ultra-high performances or static IP address (layer 4)
+* Network LB - ultra-high performances or static IP address (layer 4)<br>
-  * Classic LB - low costs, good for test or dev environments (retired by August 15, 2022)
+* Classic LB - low costs, good for test or dev environments (retired by August 15, 2022)<br>
-  * Gateway LB - transparent network gateway and and distributes traffic such as firewalls, intrusion detection and prevention systems, and deep packet inspection systems. (layer 3)
+* Gateway LB - transparent network gateway and and distributes traffic such as firewalls, intrusion detection and prevention systems, and deep packet inspection systems. (layer 3)<br>
+</b></details>
+
+<details>
+<summary>Which type of AWS load balancer is used in the following drawing?<br>
+<img src="images/aws/identify_load_balancer.png" width="300x;" height="400px;"/>
+</summary><br><b>
+
+Application Load Balancer (routing based on different endpoints + HTTP is used).
+</b></details>
+
+<details>
+<summary>What are possible target groups for ALB (Application Load Balancer)?</summary><br><b>
+
+* EC2 tasks
+* ECS instances
+* Lambda functions
+* IP Addresses
+</b></details>
+
+<details>
+<summary>True or False? ALB can route only to a single route group</summary><br><b>
+
+False. ALB can route to multiple target groups.
+</b></details>
+
+<details>
+<summary>True or False? Network load balancers operate in layer 4</summary><br><b>
+
+True. They forward TCP, UDP traffic.
 </b></details>
 
 #### AWS Security
@@ -1915,6 +2003,14 @@ Amazon definition: "AWS OpsWorks is a configuration management service that prov
 Learn more about it [here](https://aws.amazon.com/opsworks)
 </b></details>
 
+<details>
+<summary>What is AWS Snowmobile?</summary><br><b>
+
+"AWS Snowmobile is an Exabyte-scale data transfer service used to move extremely large amounts of data to AWS."
+
+Learn more [here](https://aws.amazon.com/snowmobile)
+</b></details>
+
 <details>
 <summary>What is AWS Athena?</summary><br><b>
 
@@ -2026,6 +2122,15 @@ AWS definition: "Amazon Simple Queue Service (SQS) is a fully managed message qu
 Learn more about it [here](https://aws.amazon.com/sqs)
 </b></details>
 
+#### AWS - High Availability
+
+<details>
+<summary>What high availability means from AWS perspective?</summary><br><b>
+
+* Application/Service is running in at least 2 availability zones
+* Application/Service should survive (= operate as usual) a data center disaster
+</b></details>
+
 #### AWS - Production
 
 <details>
@@ -2042,8 +2147,36 @@ One way is through launching a new instance. In more detail:
   ...
 </b></details>
 
+<details>
+<summary>You try to use an detached EBS volume from us-east-1b in us-east-1a, but it fails. What might be the reason?</summary><br><b>
+
+EBS volumes are locked to a specific availability zone. To use them in another availability zone, you need to take a snapshot and restore it in the destination availability zone.
+</b></details>
+
 <details>
 <summary>When you launch EC2 instances, it takes them time to boot due to commands you run with user data. How to improve instances boot time?</summary><br><b>
 
 Consider creating customized AMI with the commands from user data already executed there. This will allow you launch instance instantly.
 </b></details>
+
+<details>
+<summary>You try to mount EFS on your EC2 instance and it doesn't work (hangs...) What might be a possible reason?</summary><br><b>
+
+Security group isn't attached to your EFS or it lacks a rule to allow NFS traffic.
+</b></details>
+
+<details>
+<summary>How to migrate an EBS volume across availability zones?</summary><br><b>
+
+1. Pause the application
+2. Take a snapshot of the EBS volume
+3. Restore the snapshot in another availability zone
+</b></details>
+
+<details>
+<summary>How to encrypt an unencrypted EBS volume attached to an EC2 instance?</summary><br><b>
+
+1. Create EBS snapshot of the volume
+2. Copy the snapshot and mark the "Encrypt" option
+3. Create a new EBS volume out of the encrypted snapshot
+</b></details>

exercises/aws/alb_multiple_target_groups.md

@@ -0,0 +1,15 @@
+## AWS ELB - ALB Multiple Target Groups
+
+### Requirements                   
+
+Two EC2 instances with a simple web application that shows the web page with the string "Hey, it's a me, `<HOSTNAME>`!"
+One EC2 instance with a simple web application that shows the web page with the string "Hey, it's only a test..." under the endpoint /test
+
+### Objectives
+
+1. Create an application load balancer for the two instances you have, with the following properties
+  1. healthy threshold: 3
+  2. unhealthy threshold: 3
+  3. interval: 10 seconds
+2. Create another target group
+  1. Traffic should be forwarded to this group based on the "/test" path

exercises/aws/app_load_balancer.md

@@ -0,0 +1,13 @@
+## AWS ELB - Application Load Balancer 
+
+### Requirements                   
+
+Two EC2 instances with a simple web application that shows the web page with the string "Hey, it's a me, `<HOSTNAME>`!"
+
+### Objectives                     
+
+1. Create an application load balancer for the two instances you have, with the following properties
+  1. healthy threshold: 3
+  2. unhealthy threshold: 3
+  3. interval: 10 seconds
+2. Verify load balancer is working  (= you get reply from both instances at different times)

exercises/aws/create_efs.md

@@ -0,0 +1,12 @@
+## AWS - Create EFS
+ 
+### Requirements
+
+Two EC2 instances in different availability zones
+
+### Objectives
+
+1. Create an EFS with the following properties
+  1. Set lifecycle management to 60 days
+  2. The mode should match a use case of scaling to high levels of throughput and I/O operations per second
+2. Mount the EFS in both of your EC2 instances

exercises/aws/solutions/alb_multiple_target_groups.md

@@ -0,0 +1,44 @@
+## AWS ELB - ALB Multiple Target Groups
+
+### Requirements                   
+
+Two EC2 instances with a simple web application that shows the web page with the string "Hey, it's a me, `<HOSTNAME>`!"
+One EC2 instance with a simple web application that shows the web page with the string "Hey, it's only a test..." under the endpoint /test
+
+### Objectives
+
+1. Create an application load balancer for the two instances you have, with the following properties
+  1. healthy threshold: 3
+  2. unhealthy threshold: 3
+  3. interval: 10 seconds
+2. Create another target group
+  1. Traffic should be forwarded to this group based on the "/test" path
+
+### Solution
+
+#### Console
+
+1. Go to EC2 service
+2. Click in the left side menu on "Load balancers" under "Load balancing"
+3. Click on "Create load balancer"
+4. Choose "Application Load Balancer"
+5. Insert a name for the LB
+6. Choose an AZ where you want the LB to operate
+7. Choose a security group
+8. Under "Listeners and routing" click on "Create target group" and choose "Instances"
+  1. Provide a name for the target group
+  2. Set healthy threshold to 3
+  3. Set unhealthy threshold to 3
+  4. Set interval to 10 seconds
+  5. Click on "Next" and choose two out of three instances you've created
+  6. Click on "Create target group"
+9. Refresh target groups and choose the one you've just created
+10. Click on "Create load balancer" and wait for it to be provisioned
+
+11. In the left side menu click on "Target Groups" under "Load Balancing"
+12. Click on "Create target group"
+13. Set it with the same properties as previous target group but this time, add the third instance that you didn't include in the previous target group
+14. Go back to your ALB and under "Listeners" click on "Edit rules" under your current listener
+  1. Add a rule where if the path is "/test" then traffic should be forwarded to the second target group you've created
+  2. Click on "Save"
+15. Test it by going to the browser, insert the address and add "/test" to the address

exercises/aws/solutions/app_load_balancer.md

@@ -0,0 +1,35 @@
+## AWS ELB - Application Load Balancer 
+
+### Requirements
+
+Two EC2 instances with a simple web application that shows the web page with the string "Hey, it's a me, `<HOSTNAME>`!"
+
+### Objectives
+
+1. Create an application load balancer for the two instances you have, with the following properties
+  1. healthy threshold: 3
+  2. unhealthy threshold: 3
+  3. interval: 10 seconds
+2. Verify load balancer is working  (= you get reply from both instances at different times)
+
+### Solution
+
+#### Console
+
+1. Go to EC2 service
+2. Click in the left side menu on "Load balancers" under "Load balancing"
+3. Click on "Create load balancer"
+4. Choose "Application Load Balancer"
+5. Insert a name for the LB
+6. Choose an AZ where you want the LB to operate
+7. Choose a security group
+8. Under "Listeners and routing" click on "Create target group" and choose "Instances"
+  1. Provide a name for the target group
+  2. Set healthy threshold to 3
+  3. Set unhealthy threshold to 3
+  4. Set interval to 10 seconds
+  5. Click on "Next" and choose the two of the instances you've created
+  6. Click on "Create target group"
+9. Refresh target groups and choose the one you've just created
+10. Click on "Create load balancer" and wait for it to be provisioned
+11. Copy DNS address and paste it in the browser. If you refresh, you should see different message based on the instance where the traffic was routed to

exercises/aws/solutions/create_efs.md

@@ -0,0 +1,27 @@
+## AWS - Create EFS
+ 
+### Requirements
+
+Two EC2 instances in different availability zones
+
+### Objectives
+
+1. Create an EFS with the following properties
+  1. Set lifecycle management to 60 days
+  2. The mode should match a use case of scaling to high levels of throughput and I/O operations per second
+2. Mount the EFS in both of your EC2 instances
+ 
+### Solution
+ 
+1. Go to EFS console
+2. Click on "Create file system"
+3. Create on "customize"
+  1. Set lifecycle management to "60 days since last access"
+  2. Set Performance mode to "MAX I/O" due to the requirement of "Scaling to high levels of throughput"
+  3. Click on "Next"
+  4. Choose security group to attach (if you don't have any, create one and make sure it has a rule to allow NFS traffic) and click on "Next" until you are able to review and create it
+5. SSH into your EC2 instances
+  1. Run `sudo yum install -y amazon-efs-utils`
+  2. Run `mkdir efs`
+  3. If you go to your EFS page and click on "Attach", you can see what ways are there to mount your EFS on your instancess
+    1. The command to mount the EFS should be similar to `sudo mount -t efs -o tls <EFS name>:/ efs` - copy and paste it in your ec2 instance's OS