Get Block Storage with Amazon EBS

Learning Objectives

After completing this unit, you’ll be able to:

• Describe the function of Amazon Elastic Block Store (EBS) on AWS.
  
• Identify and explain the benefits of Amazon EBS.
  
• Determine which Amazon EBS volume is right for your use case.
  

You selected the default storage option when you created your Amazon EC2 instance and now you need to know how to add more storage. Since you are looking to store data associated with your EC2 instance, you need storage that is similar to a hard drive. 

In AWS, you use Amazon Elastic Block Storage (EBS) to provision these drives.

What Is Amazon EBS?

As the name implies, Amazon EBS is a block-level storage device that you can attach to an Amazon EC2 instance. These storage devices are called Amazon EBS volumes. EBS volumes are essentially drives of a user-configured size attached to an EC2 instance, similar to how you might attach an external drive to your laptop. 

EBS volumes act similarly to external drives in more than one way.

• Most Amazon EBS volumes can only be connected with one computer at a time. Most EBS volumes have a one-to-one relationship with EC2 instances, so they cannot be shared by or attached to multiple instances at one time.
  

Recently, AWS announced the Amazon EBS multi-attach feature that enables volumes to be attached to multiple EC2 instances at one time. This feature is not available for all instance types and all instances must be in the same Availability Zone. Read more about this scenario in the EBS documentation.

• You can detach an EBS volume from one EC2 instance and attach it to another EC2 instance in the same Availability Zone, to access the data on it.
  
• The external drive is separate from the computer. That means, if an accident happens and the computer goes down, you still have your data on your external drive. The same is true for EBS volumes.
  

There is another type of block storage in AWS called instance store. Instance store exists on the instance, tying the life of your data to the life of your EC2 instance. If you delete your instance, the instance store is deleted as well. Due to this, instance store is considered ephemeral storage. Read more about it in the AWS documentation. 

• You’re limited to the size of the external drive, since it has a fixed limit to how scalable it can be. For example, you may have a 2 TB external drive and that means you can only have 2 TB of content on there. This relates to EBS as well, since volumes also have a max limitation of how much content you can store on the volume.
  

Scale Amazon EBS Volumes

You can scale Amazon EBS volumes in two ways. 

1. Increase the volume size, as long as it doesn’t increase above the maximum size limit. For EBS volumes, the maximum amount of storage you can have is 16 TB. That means if you provision a 5 TB EBS volume, you can choose to increase the size of your volume until you get to 16 TB.
   
2. Attach multiple volumes to a single Amazon EC2 instance. EC2 has a one-to-many relationship with EBS volumes. You can add these additional volumes during or after EC2 instance creation to provide more storage capacity for your hosts.
   

Amazon EBS Use Cases

Amazon EBS is useful when you need to retrieve data quickly and have data persist long-term. Volumes are commonly used in the following scenarios. 

• Operating systems: Boot/root volumes to store an operating system. The root device for an instance launched from an Amazon Machine Image (AMI) is typically an Amazon EBS volume. These are commonly referred to as EBS-backed AMIs, as mentioned in AWS Compute.
  
• Databases: A storage layer for databases running on Amazon EC2 that rely on transactional reads and writes.
  
• Enterprise applications: Amazon EBS provides reliable block storage to run business-critical applications.
  
• Throughput-intensive applications: Applications that perform long, continuous reads and writes.
  

Know the Amazon EBS Volume Types

There are two main categories of Amazon EBS volumes: solid-state drives (SSDs) and hard-disk drives (HDDs). SSDs provide strong performance for random input/output (I/O), while HDDs provide strong performance for sequential I/O. AWS offers two types of each.

The following chart can help you decide which EBS volume is the right option for your workload.

Since your cat photo application is a low-latency interactive app, and you want a balance between price and performance, the best choice for the use case is the EBS General Purpose SSD (gp2) volume. For this application, you don’t need the performance of an io1 drive, the throughput-intensive benefits of the st1 drive, or the cost benefits of the sc1 drive. The gp2 is the best choice. 

Benefits of Using Amazon EBS

Here are the following benefits of using Amazon EBS (in case you need a quick cheat sheet).

• High availability: When you create an EBS volume, it is automatically replicated within its Availability Zone to prevent data loss from single points of failure.
  
• Data persistence: The storage persists even when your instance doesn’t.
  
• Data encryption: All EBS volumes support encryption.
  
• Flexibility: EBS volumes support on-the-fly changes. You can modify volume type, volume size, and input/output operations per second (IOPS) capacity without stopping your instance.
  
• Backups: Amazon EBS provides you the ability to create backups of any EBS volume.
  

Back Up Your Data

Errors happen. One of those errors is not backing up data, and then, inevitably losing that data. To prevent this from happening to you, you should back up your data—even in AWS.

Since your EBS volumes consist of the data from your Amazon EC2 instance, you’ll want to take backups of these volumes, called snapshots.

EBS snapshots are incremental backups that only save the blocks on the volume that have changed after your most recent snapshot. For example, if you have 10 GB of data on a volume, and only 2 GB of data have been modified since your last snapshot, only the 2 GB that have been changed are written to Amazon Simple Storage Service (Amazon S3).

When you take a snapshot of any of your EBS volumes, these backups are stored redundantly in multiple Availability Zones using Amazon S3. This aspect of storing the backup in Amazon S3 will be handled by AWS, so you won’t need to interact with Amazon S3 to work with your EBS snapshots. You simply manage them in the EBS console (which is part of the EC2 console).

EBS snapshots can be used to create multiple new volumes, whether they’re in the same Availability Zone or a different one. When you create a new volume from a snapshot, it’s an exact copy of the original volume at the time the snapshot was taken.

Wrap Up

You can create a new Amazon EBS volume or modify an existing EBS volume to add additional storage to your Amazon EC2 instance. Keep in mind that Amazon EBS is considered a long-term persistent block storage service. While Amazon EBS is ideal for storing the files needed in the cat photo application, it might not be great for storing cat photos due to size and sharing limitations. In the next unit, you learn more about Amazon S3 and how it can help you with your cat photo application.

Resources

• External Site: AWS: Amazon Elastic Block Store (Amazon EBS)
• External Site: AWS: Amazon EBS volume types
• External Site: AWS: Amazon EBS FAQs