Understanding AWS Instance Store
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An instance store provides temporary block-level storage for an Amazon EC2 instance. An instance store is disk storage that is physically attached to the host computer for an EC2 instance and therefore has the same lifespan as the instance. When the instance is terminated, you lose any data in the instance store. Think of it like a local hard drive for your virtual machine.
Key Characteristics of Instance Store
Temporary Storage: Instance Store volumes are non-persistent, meaning that the data stored on them will be lost if the instance is stopped, terminated, or if it fails. This storage is intended for temporary data such as caches, buffers, or other temporary files that can be recreated easily.
Local to the Instance: Instance store volumes are physically attached to the same host as the EC2 instance. This provides low latency for data access but makes the data unavailable if the instance is moved to a different host.
High Performance: Instance Store volumes typically offer higher performance compared to Amazon EBS (Elastic Block Store) volumes, especially for I/O-intensive operations. This is because Instance Store volumes are directly attached to the underlying hardware of the EC2 instance.
Not Suitable for Persistent Storage: Due to the non-persistent nature of Instance Store volumes, they are not suitable for storing critical or important data that needs to be retained even if the instance is stopped or terminated. For persistent storage needs, Amazon EBS volumes are typically recommended.
Use Cases: Instance Store volumes are often used for temporary data storage, high-performance computing (HPC) workloads, big data processing, and other scenarios where high-speed, temporary storage is required.
Cost-effective: The cost of instance store is bundled with the EC2 instance pricing, making it a good option for short-lived workloads where persistent storage isn't necessary.
Conclusion
Despite its benefits, it's important to note that Instance Store has limitations, primarily its non-persistent nature. Data stored on Instance Store volumes will be lost if the EC2 instance is stopped, terminated, or if it fails. Therefore, it's crucial to use Instance Store only for data that can be easily recreated or is not critical for long-term retention. For workloads that require data persistence, Amazon EBS volumes or other persistent storage solutions should be used instead.
Difference between Amazon Elastic Block Storage and Instance Store
| Feature | Amazon EBS | Instance Store |
| Storage Type | Block storage | Local storage on the instance |
| Persistence | Persistent | Non-persistent (ephemeral) |
| Durability | Highly durable | Not durable; data can be lost if an instance fails or is stopped |
| Snapshot | Yes (point-in-time backups) | Not available |
| Encryption | Yes | No |
| Performance | Consistent performance | Performance can vary based on instance type and workload |
| Volume Type | SSD (gp2, io1), HDD (st1, sc1) | Depends on instance type and generation |
| Resize | Yes (online) | Not available for instance stores |
| Backup | Snapshots | Not applicable |
| Use Cases | Databases, boot volumes, long-term storage | Temporary data, cache, scratch space |
| Cost | Pay for provisioned capacity (size and performance) | No additional cost beyond the instance cost |
| Availability Zone | Available in any AZ within a region | Tied to a specific instance in an AZ |
| Advantages | Data persistence, backup, scalability | High I/O performance, low latency |
| Disadvantages | Additional cost, single point of failure | Data loss risk, limited use cases |