Concepts
Overview:
Ephemeral storage refers to temporary data storage that is not meant to last beyond the life of the instance it’s attached to. When the instance stops, terminates, or fails, all the data in ephemeral storage is lost.
Characteristics:
- Temporary: Data is lost when the instance is stopped or terminated.
- Fast: Typically, this storage is directly attached to the host machine, providing lower latency and higher I/O performance.
- Not Backed Up: There is no automatic backup; users are responsible for the persistence of the data if needed.
Use Cases:
- Caching: Ephemeral storage is ideal for caches, such as Redis or Memcached.
- Temporary Data: Useful for storing temporary data like session states, intermediate results in data processing, or temporary files in batch jobs.
- Buffer: Serves as a buffer to hold incoming data during processing or batch jobs.
Examples:
AWS instance store volumes provide ephemeral storage to EC2 instances.
Persistent Data Storage
Overview:
Persistent storage, unlike ephemeral storage, retains data independently of the life cycle of any particular instance. This data is durable and stays intact across instance failures or restarts.
Characteristics:
- Durable: Data is preserved even if the instance stops, terminates, or fails.
- Backed Up: Systems like Amazon EFS and Amazon RDS provide automatic backup features and snapshot capabilities.
- Independently Scalable: Storage capacity can be adjusted without affecting running instances.
Use Cases:
- Databases: Persistent storage is a requirement for relational and NoSQL databases that need to maintain state.
- File Storage: Used for storing files, user data, and application-specific data that should not be lost.
- Enterprise Applications: Critical applications that require data to be preserved for reporting, compliance, and business intelligence among other reasons.
Examples:
Amazon Elastic Block Store (EBS) volumes provide persistent block storage for EC2 instances.
Amazon RDS is a managed relational database service with persistent storage.
Amazon S3 is an object storage service that offers high durability for storing critical data.
Comparison Table
| Feature | Ephemeral Storage | Persistent Storage |
|---|---|---|
| Data Lifetime | Instance lifetime (temporary) | Independent of instance (permanent) |
| Performance | High (local to the host machine) | Variable (network attached) |
| Backup and Recovery | None provided by default | Automated backups and snapshots |
| Scalability | Limited to instance type | Easy to scale independently |
| Cost | Generally lower | Higher with added durability |
| Use Cases | Caching, temporary data, buffering | Databases, file storage, enterprise applications |
In conclusion, when developing and architecting systems on AWS, it is essential to choose the storage pattern that aligns with your application’s requirements for data durability and lifecycle. Ephemeral storage like instance stores can offer high performance for temporary data, while persistent options like EBS, RDS, and S3 are critical for long-term data storage with reliability and durability guarantees. Understanding these differences arms candidates with the knowledge to make informed decisions and design effective AWS solutions, an important part of the AWS Certified Developer – Associate certification exam.
Answer the Questions in Comment Section
True/False: Ephemeral storage persists between instance restarts.
- True
- False
Answer: False
Explanation: Ephemeral storage is temporary and the data is lost when the instance is stopped or terminated.
Which AWS service provides persistent data storage?
- Amazon EBS (Elastic Block Store)
- Instance Store
- Amazon EC2
- Amazon S3
Answer: Amazon EBS (Elastic Block Store)
Explanation: Amazon EBS provides persistent block storage volumes for use with Amazon EC2 instances.
True/False: Instance Store volumes can be detached and reattached to another instance.
- True
- False
Answer: False
Explanation: Instance Store volumes are physically attached to the host computer, so they cannot be detached and reattached to another instance.
In which scenario might you choose ephemeral storage over persistent storage? (Select two)
- When data durability is a top priority
- For temporary storage of data that is replicated across a system
- When you need to store data that should survive instance failures
- To reduce storage costs for transient data processing
Answer: 2 and 4
Explanation: Ephemeral storage is suitable for temporary data and can help reduce costs, but it is not designed for data that must survive instance failures or requires high durability.
True/False: Data on Amazon EBS volumes is automatically replicated within the same Availability Zone.
- True
- False
Answer: True
Explanation: Amazon EBS provides the ability to have data automatically replicated within the same Availability Zone to ensure durability.
Which data storage is suitable for high-frequency read-write operations with low-latency requirements?
- EBS Provisioned IOPS (SSD)
- Magnetic Storage
- Instance Store
- Amazon S3
Answer: Instance Store
Explanation: Instance Store provides low latency and is suitable for high-frequency read-write operations, although data on Instance Store is ephemeral.
True/False: Amazon S3 can be considered as ephemeral storage.
- True
- False
Answer: False
Explanation: Amazon S3 is designed to provide 999999999% (11 9’s) of durability, making it a persistent storage service.
Persistent storage is typically more expensive than ephemeral storage. Is this statement:
- True
- False
Answer: True
Explanation: Persistent storage often comes with added features like replication and backup capabilities, which can make it more expensive than ephemeral storage.
When would it be appropriate to use Amazon EBS with EC2 instead of instance store volumes?
- When data must be retained long-term
- For temporary data processing tasks
- When cost savings are the only consideration
- During the initial boot process of an EC2 instance
Answer: When data must be retained long-term
Explanation: Amazon EBS is persistent storage and is suitable for scenarios where data must be retained beyond the lifetime of a single instance.
True/False: Data on ephemeral storage can be easily backed up to Amazon S3 for persistent storage.
- True
- False
Answer: True
Explanation: Although ephemeral storage is temporary, data can be manually backed up to Amazon S3, which is persistent storage.
Ephemeral storage is also known as:
- Durable storage
- Instance store
- Object storage
- Volume storage
Answer: Instance store
Explanation: Ephemeral storage is another term for instance store, which is directly attached to the host machine and is temporary.
Which of the following is a key characteristic of persistent storage?
- It is temporary and bound to the lifespan of an instance.
- It cannot be stopped and restarted without data loss.
- It typically offers higher performance than ephemeral storage.
- Data is not lost when the instance is stopped or terminated.
Answer: Data is not lost when the instance is stopped or terminated.
Explanation: Persistent storage retains data regardless of the state of the instance, meaning data is not lost upon stopping or terminating the instance.
Thanks for the insightful post! I always wondered what the main differences between ephemeral and persistent storage patterns were.
In AWS, ephemeral storage is often seen in EC2 instance storage. It’s temporary and associated with the lifecycle of an instance.
For persistent storage, services like EBS or S3 are commonly used. They retain data irrespective of the lifecycle of any specific instance.
Can someone explain how EFS fits into this discussion?
This blog is really helpful for my AWS Certification studies. Thanks!
I have a doubt. Does RDS use persistent or ephemeral storage?
A quick question: what’s the cost difference between using S3 and EBS for persistent storage?
Great explanation on ephemeral storage, it cleared up a lot of confusion for me!