Block storage, in cloud computing, is a type of data storage typically used in storage area network (SAN) environments where data is stored in volumes, also known as blocks. Each block acts as an individual hard drive and is configured by the storage administrator. In cloud environments, block storage volumes can be attached to cloud servers to provide expandable storage capacity.
For applications requiring low latency, high throughput, or where data must be quickly accessed via a network, block storage is an ideal solution. Examples include databases, ERP systems, and applications that need to perform transactions quickly like those in the banking or e-commerce sectors.
AWS Block Storage Options: Amazon EBS vs. Instance Store
Amazon provides two types of block storage solutions: Amazon Elastic Block Store (Amazon EBS) and Instance Store.
Amazon Elastic Block Store (Amazon EBS)
Amazon EBS provides persistent block storage volumes for use with Amazon EC2 instances. It’s designed to offer high availability and reliability, with volumes automatically replicated within its Availability Zone to prevent any single component failure.
The key characteristics of Amazon EBS include:
- Persistence: Even after an EC2 instance is terminated, the EBS volume persists.
- Backups: You can take snapshot backups of these volumes.
- Flexibility: Amazon EBS volumes can be increased in size, changed on the fly, and moved between instances.
Consider being more cost-effective, Amazon EBS is recommended when data must be quickly accessible and require long-term persistence.
Example use-case: An e-commerce application storing transaction databases would benefit from Amazon EBS for its high persistence and backup capabilities.
Instance Store
Instance Store provides temporary block-level storage for instances. This storage is located on disks that are physically attached to the host computer. Instance Store is ideal for temporary storage of information that changes frequently, such as buffers and caches.
Key characteristics of Instance Store include:
- Temporary Storage: Data stored on instance store volumes is lost if the instance is stopped, terminated, or if it fails.
- No backup: Data cannot be backed up unless manually set by the user.
- High performance: Provides high IOPS making it ideal for transactional data.
Given its transient nature, Instance Store is recommended for temporary data such as session data, cache files and other data that is recoverable.
Example use-case: A Content Delivery Network (CDN) could use instance store to cache web content closer to users, as it provides high IOPS and data can be regenerated.
Conclusion
Determining the right storage solution depends on your specific needs related to performance, cost, data durability, and size. Both Amazon EBS and Instance Store provide robust solutions for differing scenarios. Understanding these offerings and identifying the right fit for your use case is crucial not just for the AWS Certified Cloud Practitioner (CLF-C02) exam but also for efficiently architecting systems on Amazon Web Services.
Practice Test
True/False: Amazon Elastic Block Store (Amazon EBS) offers persistent block storage for Amazon Elastic Compute Cloud (EC2).
- Answer: True
Explanation: Amazon EBS is a durable, block-level storage volume that you can attach to a single EC2 instance.
Single select: What is the primary benefit of using Amazon EBS?
- a) Shared storage
- b) Disaster recovery
- c) Scalability
- d) Flexibility
- Answer: d) Flexibility
Explanation: Amazon EBS allows you to create storage volumes and attach them to Amazon EC2 instances. You can create and delete volumes, and see how much each volume is being used.
Multiple select: Which of the following are types of Amazon EBS volumes? Select all that apply.
- a) General Purpose SSD (gp2)
- b) Cold HDD (sc1)
- c) Throughput Optimized HDD (st1)
- d) Provisioned IOPS SSD (io1)
- Answer: a) General Purpose SSD (gp2), b) Cold HDD (sc1), c) Throughput Optimized HDD (st1), d) Provisioned IOPS SSD (io1)
Explanation: All four are current Amazon EBS volume types, each designed for different use cases.
True/False: Amazon EC2 instance store volumes persist independently from the life of an instance.
- Answer: False
Explanation: An instance store provides temporary block-level storage for instances. This storage is located on disks that are physically attached to the host computer and persist only for the life of the instance.
Single select: What would you use an instance store for?
- a) To perform a database or system backup
- b) To create an application that needs to scale with growth
- c) To store data that is continually updating
- d) To temporarily store data that changes rapidly
- Answer: d) To temporarily store data that changes rapidly
Explanation: Instance stores assure short-term, high-performance storage that is ideal for data that changes rapidly, like buffers, caches, and scratch data.
Multiple select: Which of the following are benefits of Amazon EBS? Select all that apply.
- a) Scalability
- b) Durability
- c) Flexibility
- d) Speed
- Answer: a) Scalability, b) Durability, c) Flexibility
Explanation: Amazon EBS provides benefits including scalability, durability, and flexibility.
True/False: EBS-optimized instances are designed for use with both Standard and Provisioned IOPS Amazon EBS volumes.
- Answer: True
Explanation: EBS-optimized instances deliver dedicated throughput between Amazon EC2 and Amazon EBS, with options between 500 Megabits per second and 1,000 Megabits per second depending on the instance type used.
Single select: Which AWS block storage service would be best for working with databases?
- a) Amazon S3
- b) Amazon Glacier
- c) Amazon EBS
- d) Instance store
- Answer: c) Amazon EBS
Explanation: Amazon EBS volumes are network-attached, and persist independently from the life of an instance, making them suitable for databases that require quick access.
Multiple select: Which of the following are valid use cases for instance store volumes? Select all that apply.
- a) Swap memory
- b) Data that needs to persist beyond the life of an instance
- c) Temporary storage of information
- d) Buffering
- Answer: a) Swap memory, c) Temporary storage of information, d) Buffering
Explanation: Instance store volumes are ideal for temporary storage of data and for swap memory, but not fit for data persistence.
True/False: Instance store supports all the EC2 instances.
- Answer: False
Explanation: Not all Amazon EC2 instances come with instance storage. Certain instance types do not support instance stores.
Interview Questions
What is Amazon Elastic Block Store (Amazon EBS)?
Amazon EBS is a scalable block storage service designed for use with Amazon EC2 instances. It provides low-latency performance needed to run your workloads.
What are the different volume types offered by Amazon EBS?
The different volume types offered by Amazon EBS are: General Purpose SSD (gp2), Provisioned IOPS SSD (io1 & io2), Throughput Optimized HDD (st1), Cold HDD (sc1), and Magnetic (standard).
What is an instance store in AWS?
An instance store provides temporary block-level storage for instance. The data on an instance store volume persists only during the life of its associated instance.
How is data persistency different between Amazon EBS and an instance store?
The data on an Amazon EBS volume persists independently of the life of the instance, while data on instance store volumes is deleted when you stop or terminate the instance.
How does the performance of Amazon EBS and instance stores compare?
Generally, instance store volumes can provide a high input/output operations per second (IOPS), but EBS volumes are designed to offer durability, and ease at snapshotting and cloning.
In what scenario would you use instance store instead of Amazon EBS?
Instance store is optimal for temporary storage, for data that changes frequently, or for components that are replicated across a fleet of instances.
Can you attach multiple EBS volumes to a single EC2 instance?
Yes, you can attach multiple EBS volumes to a single EC2 instance.
Can you attach a single EBS volume to multiple EC2 instances?
No, you can’t attach a single EBS volume to multiple EC2 instances.
Can an Amazon EBS volume and an EC2 instance exist in separate Availability Zones?
No, an EBS volume can only be attached to an instance in the same Availability Zone.
What is an EBS snapshot?
An EBS snapshot is a point-in-time copy of your data that you can use to enable disaster recovery, migrate across regions and accounts, improve backup compliance, or create clones for test and development environments.
How do you protect the data in your EBS volumes against failures?
You can create snapshots of your EBS volumes, which are stored on Amazon S3, and are automatically encrypted i.e., to protect against failure.
Are Amazon EBS volumes automatically encrypted?
No, EBS volumes are not automatically encrypted. Encryption needs to be selected while creating the volume.
How are EBS volume IO rates determined?
The IO rates of EBS volumes are determined by their size, the volume type, and the IOPS provisioned for the volumes.
Can an EBS SSD volume be converted to an HDD volume and vice versa?
An EBS volume’s type can be changed by creating a snapshot of the volume to back up the data, and then creating a new volume of the desired type from the snapshot.
Can Amazon EBS and Amazon S3 be used for the same tasks?
While both EBS and S3 are storage solutions, they differ in their use cases. EBS is a block-level storage suitable for EC2 instances, while S3 is an object storage service suitable for static files which are globally distributed.
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