Questions
8 of 11
1What is Amazon EBS?
2What is an EBS volume?
3Discuss EBS volume types.
4How to create and attach an EBS volume to an EC2 instance?
5How do EBS snapshots work?
6What is an EBS snapshot archive?
7Discuss the Recycle Bin for EBS snapshots.
8Discuss fast snapshot restore (FSR) for EBS snapshots.
9Discuss the multi-attach feature in Amazon EBS.
10Discuss EBS encryption.
11Which of the EBS volume types can be used as boot volumes when you create EC2 instances?
AWS-EC2AWS-EC2
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EBS
EFS
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08 / 11

Discuss fast snapshot restore (FSR) for EBS snapshots.

Difficulty: 7/10
Fast Snapshot Restore, EBS snapshot performance, Cost trade-offs

Fast Snapshot Restore (FSR) is an EBS feature that eliminates the I/O latency penalty when creating a new volume from a snapshot. Without FSR, a restored volume lazy-loads its data — blocks are fetched from S3 on first access, causing slow performance. With FSR enabled, the volume delivers its full provisioned performance immediately upon creation.

Normally when you create an EBS volume from a snapshot, the volume is created instantly but its data blocks are fetched from Amazon S3 in the background as they are accessed for the first time. This lazy-loading behavior causes high latency and low IOPS on first access — which is a serious problem for databases and production workloads that need immediate full performance. Fast Snapshot Restore pre-warms the data so volumes are fully initialized from the moment of creation.

How FSR Works
  1. 1

    When FSR is enabled on a snapshot for a specific AZ, AWS pre-initializes the snapshot data in a dedicated internal cache

  2. 2

    Volumes created from FSR-enabled snapshots deliver full provisioned IOPS and throughput immediately — no warm-up required

  3. 3

    FSR must be enabled per snapshot, per Availability Zone separately

  4. 4

    There is a limit of 50 FSR-enabled snapshots per region by default (can be increased via AWS Support)

  5. 5

    FSR has an additional hourly cost per snapshot per AZ (~$0.75 per snapshot per AZ per hour)

Without FSR vs With FSR
  1. 1

    Without FSR — Volume is created instantly but I/O performance is degraded on cold blocks. A workaround is to pre-warm the volume using dd or fio to read all blocks before production use.

  2. 2

    Without FSR (workaround) — Use the dd command: sudo dd if=/dev/xvdf of=/dev/null bs=1M to pre-warm all blocks before putting the instance in service.

  3. 3

    With FSR — Volume is fully initialized at creation. No pre-warming needed. Immediate full IOPS and throughput. Critical for Auto Scaling scenarios.

  4. 4

    Best for — Auto Scaling Groups that need to launch instances quickly with pre-populated data volumes, disaster recovery scenarios, and test environments restored from production snapshots.

Enabling and Managing Fast Snapshot Restore via AWS CLI

Scenario Questions

0-2 years experience

  1. 1You need to restore a 200 GB EBS volume from a snapshot and the application expects sub‑second latency. How would you use Fast Snapshot Restore to meet that requirement?
  2. 2If you enable Fast Snapshot Restore on a snapshot in one AZ but try to attach the volume in another AZ, what will happen and how would you handle it?
  3. 3What steps would you take to verify that Fast Snapshot Restore is actually being used after you launch an instance?

2-5 years experience

  1. 1Your team enabled Fast Snapshot Restore on a critical database snapshot, but after deployment the restore time is still high. What could be causing the slowdown and how would you troubleshoot?
  2. 2When deciding whether to enable Fast Snapshot Restore for a set of nightly backup snapshots, what cost and performance trade‑offs would you consider?
  3. 3Explain how you would automate the enablement of Fast Snapshot Restore across multiple regions for a CI/CD pipeline.

5-8 years experience

  1. 1Design a solution for a multi‑AZ, high‑availability service that needs to restore large EBS volumes within seconds after a failure. Discuss how you would incorporate Fast Snapshot Restore, replication, and any fallback mechanisms.
  2. 2At scale, enabling Fast Snapshot Restore on thousands of snapshots can hit service limits. How would you architect a system to manage those limits while ensuring SLA compliance?
  3. 3What are the implications of Fast Snapshot Restore on snapshot consistency and how would you ensure data integrity during rapid restores?

8+ years experience

  1. 1Your organization is migrating legacy workloads that rely on slow snapshot restores to a new architecture using Fast Snapshot Restore. What cross‑team considerations (cost, security, operational processes) would you address to make the migration successful?
  2. 2How would you evaluate the long‑term financial impact of enabling Fast Snapshot Restore for all production snapshots versus a selective approach, and how would you present this to leadership?
  3. 3Propose a governance model for managing Fast Snapshot Restore permissions and lifecycle across multiple business units in a large enterprise.

Follow-up Questions

  • What monitoring would you put in place to confirm FSR is active?
  • How would you handle a situation where enabling FSR exceeds your account limits?
  • Can you describe a scenario where you would choose not to use FSR despite its performance benefits?
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