Instance Stores in AWS
Instance Stores in AWS
Instance stores in AWS are temporary block-level storage that is physically attached to the host server running an EC2 (Elastic Compute Cloud) instance. Unlike Amazon EBS (Elastic Block Store), instance store volumes do not persist beyond the lifetime of the instance. When an EC2 instance is stopped or terminated, the data on the instance store is lost.
Instance stores are typically used for temporary storage of data that doesn’t need to persist after an instance stops or terminates, such as caching, buffers, or data that can be regenerated easily.
Key Characteristics of Instance Stores
Ephemeral Storage:
Data stored on instance stores is ephemeral, meaning it only exists for the life of the instance. When an instance is stopped or terminated, the data on the instance store is lost.
Performance:
Instance stores are physically attached to the host server, which generally provides low-latency, high-throughput performance. This makes instance stores ideal for temporary storage with high-performance requirements, such as cache or buffers.
No Data Persistence:
Instance stores do not persist data after an instance is terminated or stopped. Data recovery is not possible unless you have backed it up to a persistent storage solution like Amazon S3 or EBS.
Attached at Launch:
Instance store volumes are available only on certain EC2 instance types (known as instance store-backed instances). These volumes are attached to the instance when it is launched, and they cannot be added or removed while the instance is running.
Data Volatility:
Since the data is not persisted across instance stops or terminations, instance stores are not suitable for long-term storage or storage of critical data.
Types of Instance Store Volumes
Instance Store-Backed Volumes:
Some EC2 instance types come with local instance store volumes. These are automatically included in the instance configuration and are usually used for high-performance, low-latency tasks.
NVMe Instance Stores:
Many newer EC2 instance types, particularly those optimized for high-performance workloads (e.g., I3, M5d, C5d), come with NVMe (Non-Volatile Memory Express) instance stores. NVMe instance stores are high-performance SSD-backed storage and offer very low latencies compared to traditional spinning hard drives.
Use Cases for Instance Stores
Cache Storage:
Instance stores are ideal for use as cache storage for temporary data that doesn’t need to persist once the instance is stopped or terminated, such as web server caches, application caches, or session data.
Buffer Storage:
For applications that require temporary buffer storage or intermediate data processing, instance stores can be used as fast, ephemeral storage.
Scratch Space for Big Data Processing:
Instance stores are often used in distributed big data processing workloads, like Hadoop or Spark, where data is processed in chunks, and intermediate data does not need to be saved.
Temporary Storage for Compute-Intensive Tasks:
Instance stores are useful for workloads that require fast I/O, such as rendering, scientific simulations, and financial modeling, where results are stored temporarily before being saved to long-term storage.
Instance Store vs. EBS
| Feature | Instance Store | EBS (Elastic Block Store) |
|---|---|---|
| Persistence | Data is lost when the instance stops or terminates. | Data is persistent and survives instance stops or terminations. |
| Use Cases | Temporary storage (e.g., cache, buffers, scratch space). | Long-term storage (e.g., databases, file systems). |
| Performance | High performance with low latency (ideal for temporary, fast storage). | Scalable performance with provisioned IOPS (but can have higher latency). |
| Data Recovery | No data recovery after termination. | Data can be backed up, replicated, and restored. |
| Pricing | Free (included in the cost of the EC2 instance). | Charged separately based on the volume size and IOPS. |
How to Use Instance Store
Choosing Instance Store-Backed Instances:
When launching an EC2 instance, you can select the instance type that includes instance store volumes. Note that not all instance types provide instance store volumes, and availability may vary by region.
Managing Instance Store Volumes:
Unlike EBS, you cannot detach or re-attach instance store volumes from EC2 instances after they are launched. Instance store volumes are tied to the lifecycle of the EC2 instance.
Data Backup:
Since the data on instance stores is temporary, you should periodically back up any critical data to Amazon S3 or Amazon EBS to ensure it’s preserved. You can use scripts or automation to copy data from instance stores to long-term storage.
Considerations When Using Instance Stores
No Snapshots:
Instance store volumes cannot be snapshotted. If you need data persistence, it’s essential to back up your data to S3, EBS, or another permanent storage solution.
Data Loss:
Be prepared for data loss when stopping or terminating the instance. Always ensure that you back up data that needs to persist.
Instance Types with Instance Store Volumes:
Not all EC2 instance types support instance store volumes. For example, M5 and C5 instances do not have instance store volumes, while I3, D2, and R5d types do. Be sure to check the specifications of the instance type before selecting it for your use case.
Conclusion
Instance stores are a useful and cost-effective option for temporary storage with low-latency, high-throughput performance. They are best suited for tasks that require fast, ephemeral storage and where data persistence is not critical. However, if data durability or persistence is important, you should use Amazon EBS or another permanent storage service. Always back up important data to ensure its availability in case the instance is stopped or terminated.
