Ephemeral data storage is temporary by nature. The data only lasts as long as the lifespan of its parent entity, like a Docker container or EC2 instance. When the parent entity ceases to exist, the data is lost. This short-lived data storage is often implemented in microservices architectures.
An example of ephemeral storage would be instance store volumes. In AWS EC2, instance store volumes offer temporary block-level storage for instances. These are physically attached to the host computer. Keep in mind that the data in this storage is not persistent and will be lost if the instance is stopped or terminated.
# To utilize an instance store volume in AWS EC2, you’d use:
aws ec2 run-instances –image-id ami-abc12345 –count 1 –instance-type t2.micro –block-device-mappings file://mapping.json
(Note this is a sample code and ami-id provided here is not actually valid)
In this example, the data on the instance store volumes will be deleted once the instance is terminated or stopped.
Persistent Data Storage Pattern
Contrarily, persistent data storage is designed to outlast the lifespan of its parent entity. When an EC2 instance or Docker container is terminated, the data in a persistent store remains intact. The data can be recovered or accessed, even when the parent entity is non-existent.
AWS provides various services for persistent storage like Amazon S3, Amazon EFS, or Amazon RDS. One prominent example of persistent storage is Amazon Elastic Block Store (Amazon EBS), which provides block storage you can attach to EC2 instances.
For instance, in the Amazon S3, the data will exist until explicitly deleted:
# To upload an object to S3, you would:
aws s3api put-object –bucket MY_BUCKET –key MY_KEY –body MY_FILE
Distinctive Features
| Points | Ephemeral Storage | Persistent Storage |
|---|---|---|
| Lifecycle | Tied to the parent entity | Independent of the parent entity |
| Data Lifespan | Temporary | Permanent |
| AWS Services | Instance Store | S3, EBS, EFS, RDS and DynamoDB |
| Use Cases | Cache, Temporary data storage | Databases, Application Data |
To summarize, the decision between ephemeral and persistent data storage largely depends on the specific requirements of the application you’re building. Ephemeral data storage patterns are ideal for temporary data and provide faster I/O, while persistent storage is slower but better for storing critical application data long-term.
When preparing for the AWS Certified Developer – Associate (DVA-C02) exam, understanding these differences is critical when designing applications in the AWS environment. The goal is to use the right storage type for the right purpose to create efficient, cost-effective, and reliable applications.
Practice Test
Ephemeral storage preserves data even after a system restart.
- True
- False
Answer: False
Explanation: Ephemeral storage does not keep data after a system is restarted. On the contrary, persistent storage retains data even after a system restart.
Persistent data storage is not cost-effective compared to ephemeral storage.
- True
- False
Answer: True
Explanation: Persistent data storage often implies higher costs due to the infrastructure, management, and security it demands. Ephemeral storage is typically cheaper.
Which of the following is an AWS service that provides ephemeral storage?
- AWS SQS
- AWS RDS
- AWS Instance Store
- AWS S3
Answer: AWS Instance Store
Explanation: AWS Instance Store provides ephemeral storage that is attached to the compute node.
AWS S3 provides persistent storage.
- True
- False
Answer: True
Explanation: AWS S3 is a scalable object storage service that provides persistent storage.
Ephemeral storage is ideal for storing critical data that can’t be lost.
- True
- False
Answer: False
Explanation: Ephemeral storage isn’t meant for storing critical data as it is lost when instances are stopped or fail.
Which of the following is NOT a characteristic of persistent storage?
- Data survives system reboot
- Data is lost on system failure
- It is typically more expensive than ephemeral storage
- It provides storage for essential data
Answer: Data is lost on system failure
Explanation: Persistent storage retains the data even in case of system failures.
What services provide persistent storage in AWS? (Choose 2)
- Amazon RDS
- Amazon EC2 Instance store
- Amazon EBS
- Amazon SQS
Answer: Amazon RDS, Amazon EBS
Explanation: Both Amazon RDS and EBS offer persistent storage which means the data remains intact even after stopping and starting instances.
Ephemeral storage is usually faster than persistent storage.
- True
- False
Answer: True
Explanation: Since ephemeral storage is directly attached to the instance, it usually provides lower latency and higher throughput than persistent storage.
Ephemeral storage is typically used for caching data.
- True
- False
Answer: True
Explanation: Ephemeral storage is often used for caching and temporary content such as scratch space.
With persistent storage, if the AWS EC2 instance fails, the data is lost.
- True
- False
Answer: False
Explanation: The key difference between ephemeral and persistent storage is that persistent storage retains data even if the EC2 instance fails or is stopped.
Which of the following AWS services provides ephemeral storage? (Multiple Selection)
- Amazon EBS
- Amazon EC2 Instance Store
- Amazon RDS
- Amazon S3
Answer: Amazon EC2 Instance Store
Explanation: Amazon EC2 Instance Store offers ephemeral storage that is ideal for temporary storage, but not recommended for long-term storage or critical information. EBS, RDS, and S3 provide persistent data storage.
Interview Questions
What is ephemeral storage in AWS?
Ephemeral storage in AWS refers to storage that is temporary or short-lived and is deleted when an EC2 instance is stopped or terminated.
What do you understand by persistent storage in AWS?
Persistent storage in AWS is a type of storage where data is kept even after an EC2 instance is stopped or terminated. Amazon EBS (Elastic Block Store) is an example of persistent storage.
Can you identify a significant difference between ephemeral and persistent storage in AWS?
The main difference between ephemeral and persistent storage in AWS is the data lifespan – ephemeral storage erases data upon reboot, while persistent storage maintains data even after reboot.
What are the typical uses of ephemeral storage in AWS?
Ephemeral storage is generally used for applications that require significant I/O performance and can withstand data loss, such as temporary storage for raw data, cache files, or other temporary content.
What type of applications would benefit from using persistent storage in AWS?
Applications that require long-term, durable storage, such as databases or applications needing to store user-related or business-critical data, would benefit from using persistent storage.
Can you name one AWS service that provides ephemeral storage?
Amazon EC2 instance store provides ephemeral storage.
Can you name one AWS service that provides persistent storage?
Amazon EBS (Elastic Block Store) provides persistent storage.
In terms of cost, how do ephemeral and persistent storage compare in AWS?
Ephemeral storage is generally less expensive because it comes bundled with Instance storage, while persistent storage like Amazon EBS volumes are priced separately and tend to be more expensive.
Can you migrate data from ephemeral storage to persistent storage in AWS?
Yes, data can be migrated from ephemeral storage to persistent storage, but this needs to be manually configured since ephemeral storage data is not automatically moved or backed up.
How does data availability differ between ephemeral and persistent storage in AWS?
Persistent storage offers higher data availability compared to ephemeral storage since it is designed to keep data even after EC2 instances are stopped or terminated.
What are the durability levels of ephemeral and persistent storage in AWS?
Persistent storage such as Amazon EBS has an annual failure rate between 0.1% to 0.2%. In contrast, ephemeral storage has a higher risk of data loss due to instance stop, termination, or hardware failure.
How would you describe the speed of ephemeral storage versus persistent storage in AWS?
Generally, ephemeral storage like Amazon EC2 Instance Store provides a high I/O performance than most persistent storage options. However, this can vary based on the specific type of persistent storage being used.
Can you attach or detach ephemeral storage from running EC2 instances in AWS?
No, ephemeral storage cannot be attached or detached from running EC2 instances.
Can you attach or detach persistent storage from running EC2 instances in AWS?
Yes, persistent storage like Amazon EBS volumes can be attached or detached from running EC2 instances.
What happens to the ephemeral storage when an EC2 instance is resized?
Ephemeral storage data is lost when an EC2 instance is resized because stopping the instance, which is necessary for resizing, causes the ephemeral storage data to be deleted.
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