Instance storage - Amazon EMR

Instance storage

Instance store and Amazon EBS volume storage is used for HDFS data and for buffers, caches, scratch data, and other temporary content that some applications may "spill" to the local file system.

Amazon EBS works differently within Amazon EMR than it does with regular Amazon EC2 instances. Amazon EBS volumes attached to Amazon EMR clusters are ephemeral: the volumes are deleted upon cluster and instance termination (for example, when shrinking instance groups), so it's important that you not expect data to persist. Although the data is ephemeral, it is possible that data in HDFS may be replicated depending on the number and specialization of nodes in the cluster. When you add Amazon EBS storage volumes, these are mounted as additional volumes. They are not a part of the boot volume. YARN is configured to use all the additional volumes, but you are responsible for allocating the additional volumes as local storage (for local log files for example).

Other caveats for using Amazon EBS with Amazon EMR clusters are:

  • You can't snapshot an Amazon EBS volume and then restore it within Amazon EMR. To create reusable custom configurations, use a custom AMI (available in Amazon EMR version 5.7.0 and later). For more information, see Using a custom AMI.

  • An encrypted Amazon EBS root device volume is supported only when using a custom AMI. For more information, see Creating a custom AMI with an encrypted Amazon EBS root device volume.

  • If you apply tags using the Amazon EMR API, those operations are applied to EBS volumes.

  • There is a limit of 25 volumes per instance.

  • The Amazon EBS volumes on core nodes cannot be less than 5 GB.

Default Amazon EBS storage for instances

Amazon EMR automatically attaches an Amazon EBS General Purpose SSD (gp2) 10 GB volume as the root device for its AMIs to enhance performance. In addition, for EC2 instances with EBS-only storage, Amazon EMR allocates Amazon EBS storage volumes to instances. When you create a cluster using Amazon EMR release version 5.22.0 and later, the default amount of Amazon EBS storage increases based on the size of the instance. In addition, we split increased storage across multiple volumes, giving increased IOPS performance, and in turn better performance for some standardized workloads. If you want to use a different Amazon EBS instance storage configuration, you can specify it when you create an Amazon EMR cluster or add nodes to an existing cluster. See the table below to identify the default number of EBS storage volumes, their size, and the total size per instance type.

EBS costs are pro-rated by the hour based on the monthly Amazon EBS charges for gp2 volumes in the Region where the cluster runs. For example, the Amazon EBS cost per hour for the root volume on each cluster node in a Region that charges $0.10/GB/month would be approximately $0.00139 per hour ($0.10/GB/month divided by 30 days divided by 24h times 10 GB).

Default Amazon EBS storage volumes and size by instance type for Amazon EMR 5.22.0 and later
Instance size Number of volumes Volume size (GiB) Total size (GiB)

*.large

1

32

32

*.xlarge

2

32

64

*.2xlarge

4

32

128

*.4xlarge

4

64

256

*.8xlarge

4

128

512

*.9xlarge

4

144

576

*.10xlarge

4

160

640

*.12xlarge

4

192

768

*.16xlarge

4

256

1024

*.18xlarge

4

288

1152

*.24xlarge

4

384

1536

Specifying additional EBS storage volumes

When you configure instance types in Amazon EMR, you can specify additional EBS volumes to add capacity beyond the instance store (if present) and the default EBS volume. Amazon EBS provides the following volume types: General Purpose (SSD), Provisioned IOPS (SSD), Throughput Optimized (HDD), Cold (HDD), and Magnetic. They differ in performance characteristics and price, so you can tailor your storage based on the analytic and business needs of your applications. For example, some applications may have a need to spill to disk while others can safely work in-memory or using Amazon S3.

You can only attach Amazon EBS volumes to instances at cluster startup time and when you add an extra task node instance group. If an instance in an Amazon EMR cluster fails, then both the instance and attached Amazon EBS volumes are replaced with new volumes. Consequently, if you manually detach an Amazon EBS volume, Amazon EMR treats that as a failure and replaces both instance storage (if applicable) and the volume stores.