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Thursday, July 26, 2018

Amazon Elastic Block Store (EBS) FAQ



Q: What happens to my data when a system terminates?

The data stored on a local instance store will persist only as long as that instance is alive. However, data that is stored on an Amazon EBS volume will persist independently of the life of the instance. Therefore, we recommend that you use the local instance store for temporary data and, for data requiring a higher level of durability, we recommend using Amazon EBS volumes or backing up the data to Amazon S3. If you are using an Amazon EBS volume as a root partition, you will need to set the Delete On Terminate flag to "N" if you want your Amazon EBS volume to persist outside the life of the instance.

Q: What kind of performance can I expect from Amazon EBS volumes?

Amazon EBS provides four current generation volume types and are divided into two major categories: SSD-backed storage for transactional workloads and HDD-backed storage for throughput intensive workloads. These volume types differ in performance characteristics and price, allowing you to tailor your storage performance and cost to the needs of your applications. For more information on see the EBS product details page, and for additional information on performance, see the Amazon EC2 User Guide's EBS Performance section.

Q: What are Throughput Optimized HDD (st1) and Cold HDD (sc1) volume types?

ST1 volumes are backed by hard disk drives (HDDs) and are ideal for frequently accessed, throughput intensive workloads with large datasets and large I/O sizes, such as MapReduce, Kafka, log processing, data warehouse, and ETL workloads. These volumes deliver performance in terms of throughput, measured in MB/s, and include the ability to burst up to 250 MB/s per TB, with a baseline throughput of 40 MB/s per TB and a maximum throughput of 500 MB/s per volume. ST1 is designed to deliver the expected throughput performance 99% of the time and has enough I/O credits to support a full-volume scan at the burst rate.

SC1 volumes are backed by hard disk drives (HDDs) and provides the lowest cost per GB of all EBS volume types. It is ideal for less frequently accessed workloads with large, cold datasets. Similar to st1, sc1 provides a burst model: these volumes can burst up to 80 MB/s per TB, with a baseline throughput of 12 MB/s per TB and a maximum throughput of 250 MB/s per volume. For infrequently accessed data, sc1 provides extremely inexpensive storage. SC1 is designed to deliver the expected throughput performance 99% of the time and has enough I/O credits to support a full-volume scan at the burst rate.

To maximize the performance of st1 and sc1, we recommend using EBS-optimized EC2 instances.

Q: Which volume type should I choose?

Amazon EBS includes two major categories of storage: SSD-backed storage for transactional workloads (performance depends primarily on IOPS) and HDD-backed storage for throughput workloads (performance depends primarily on throughput, measured in MB/s). SSD-backed volumes are designed for transactional, IOPS-intensive database workloads, boot volumes, and workloads that require high IOPS. SSD-backed volumes include Provisioned IOPS SSD (io1) and General Purpose SSD (gp2). HDD-backed volumes are designed for throughput-intensive and big-data workloads, large I/O sizes, and sequential I/O patterns. HDD-backed volumes include Throughput Optimized HDD (st1) and Cold HDD (sc1). For more information on Amazon EBS see the EBS product details page.

Q: Do you support multiple instances accessing a single volume?

While you are able to attach multiple volumes to a single instance, attaching multiple instances to one volume is not supported at this time.

Q: Will I be able to access my EBS snapshots using the regular Amazon S3 APIs?

No, EBS snapshots are only available through the Amazon EC2 APIs.

Q: Do volumes need to be un-mounted in order to take a snapshot? Does the snapshot need to complete before the volume can be used again? 

No, snapshots can be done in real time while the volume is attached and in use. However, snapshots only capture data that has been written to your Amazon EBS volume, which might exclude any data that has been locally cached by your application or OS. In order to ensure consistent snapshots on volumes attached to an instance, we recommend cleanly detaching the volume, issuing the snapshot command, and then reattaching the volume. For Amazon EBS volumes that serve as root devices, we recommend shutting down the machine to take a clean snapshot.

Q: Are snapshots versioned? Can I read an older snapshot to do a point-in-time recovery?

Each snapshot is given a unique identifier, and customers can create volumes based on any of their existing snapshots.

Q: What charges apply when using Amazon EBS shared snapshots?

If you share a snapshot, you won’t be charged when other users make a copy of your snapshot. If you make a copy of another user’s shared volume, you will be charged normal EBS rates.

Q: Can users of my Amazon EBS shared snapshots change any of my data?

Users who have permission to create volumes based on your shared snapshots will first make a copy of the snapshot into their account. Users can modify their own copies of the data, but the data on your original snapshot and any other volumes created by other users from your original snapshot will remain unmodified.

Q: How can I discover Amazon EBS snapshots that have been shared with me?

You can find snapshots that have been shared with you by selecting “Private Snapshots” from the viewing dropdown in the Snapshots section of the AWS Management Console. This section will list both snapshots you own and snapshots that have been shared with you.

Q: How can I find what Amazon EBS snapshots are shared globally?

You can find snapshots that have been shared globally by selecting “Public Snapshots” from the viewing dropdown in the Snapshots section of the AWS Management Console.

Q: Do you offer encryption on Amazon EBS volumes and snapshots?

Yes. EBS offers seamless encryption of data volumes and snapshots. EBS encryption better enables you to meet security and encryption compliance requirements.

Q: How can I find a list of Amazon Public Data Sets?

All information on Public Data Sets is available in our Public Data Sets Resource Center. You can also obtain a listing of Public Data Sets within the AWS Management Console by choosing “Amazon Snapshots” from the viewing dropdown in the Snapshots section.

Q: Where can I learn more about EBS?

You can visit the Amazon EBS FAQ page.

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