Choosing Resilient Storage

1. What is the advantage of EFS shared storage over EBS volumes?
EFS storage has no size constraints and no sharing constraints. EBS storage skills are required, and EBS storage can be shared over up to thousands of instances across multiple availability zones.

2. Describe the difference between files stored in object storage and files stored using block storage?
Files stored in object storage such as S3 or S3 Glacier are stored and updated as entire files. In contrast, EBS storage can be updated block by block, either as storage changes or by snapshot.

3. What is the difference between EBS io2 and io1 volumes in regard to attaching the volumes to instances?
EBS io2 volumes support a feature called multi-attach, which allows you to attach the EBS volume to up to 16 instances, as long as the instances are hosted by the Nitro hypervisor.

4. What happens when an EBS snapshot is deleted in the background?
Before a snapshot is deleted, it is analyzed, and only the data that is exclusive to the snapshot copy is retained.

5. What is the fastest storage that can be ordered at AWS?    
The fastest storage that can be ordered at AWS is ephemeral storage, which is temporary storage volumes that are located on the bare-metal server where the instance is hosted. Because the instance is in exactly the same physical location, there is no network to traverse, and therefore the local storage volume is the fastest. However, the ephemeral storage is not redundant; when the instance is turned off or fails, the storage is erased.

6. In order to use most management features of S3 storage, what must first be enabled?
In order to use S3 lifecycle rules and Same-Region Replication and Cross-Region Replication, you must have versioning enabled.

7. How can S3 objects be shared to clients that do not have AWS credentials?
It is possible to share S3 objects to any person who does not have AWS credentials by creating and distributing a pre-signed URL. Temporary access is defined by configuring date and time expiration values.

8. After a WORM policy has been applied to an S3 bucket in Compliance mode, when can the policy be removed?
A WORM policy applied to an S3 bucket when operating in Compliance mode can never be removed—not even by Amazon. That’s the point of a WORM policy. However, it is usually assumed that the policy can be removed.