Chloe McAree (McAteer)
Published on

AWS Elastic Block Storage (EBS)


This is part of a blog series giving a high level overview of the different services examined on the AWS Solution Architect Associate exam, to view the whole series click here.

EBS Summary

  • EBS is persistent storage volumes for EC2.

  • EBS volumes are automatically replicated within an Availability Zone and therefore are highly available and can be used for mission critical applications.

  • Very performant and can be used for throughput intensive workloads. Storage can also be increase without disturbing any current workloads.

  • The EBS volume needs to be mounted to an EC2 instance within the same Availability Zone.

  • You can take snapshots of your volumes which are point-in-time copies, these copies can then also be restored into new regions. The snapshots themselves are stored in S3.

  • Snapshots are incremental — only blocks that have changed since your last snapshot are moved to S3. When snapshotting root device — best practice to terminate it first.

  • You can create an EBS volume as encrypted and then also any snapshot taken of that volume will therefore be encrypted as well.

Types of EBS

There are a number different types of EBS volumes all varying in price and performance, below are some more details about them:

General Purpose SSD (GP2)

  • Balances price and performance and can be used for most workloads
  • Good for up to 16,000 IOPS per volume

Provisioned IOPS SSD (IO1)

  • High performance SSD for mission critical applications
  • Commonly used for databases
  • Can go to 64,000 IOPS per volume

Throughput Optimised HDD (St1)

  • Low cost hard disk drive (magnetic storage)
  • Used for throughout intensive and frequently access workloads
  • Typically used for big data, data warehouses and log processing
  • Max 500 IOPS per volume

Cold HDD (SC1)

  • Lowest cost hard disk drive (magnetic storage)
  • Used for less frequently accessed workloads and when lowest storage cost is important.
  • Common use could be for file servers
  • Max 250 IOPS per volume

EBS Magnetic (Standard)

  • Previous generation hard disk drive typically used for infrequently accessed workloads.
  • Max 40–200 IOPS per volume

EBS Vs Instance Store

  • Instance Store can provide temporary block level storage to your instances.
  • Instance Store volumes are sometimes called Ephemeral Storage (data only persists for the lifetime of the instance it is attached to)
  • All Amazon Machine Images(AMIs) have to be backed by either EBS or Instance Store.
  • Both root devices are launched a little differently — with EBS the root device is launched from an EBS volume created by an EBS snapshot. Whereas, an instance store’s root device is created from a template stored in S3.
  • If the host fails and stops for instance store all data will be lost.
  • With EBS instance, it can be stopped and you will not lose your data — you can then reboot it.
  • Both root volumes are deleted on instance termination by default. However, with EBS you can specify to keep it on creation.