What should a solutions architect recommend?
Snapshot the EBS volumes regularly and build new volumes using those snapshots in additional Availability Zones.
Use Amazon Elastic Block Store (Amazon EBS) for the EC2 instance root volumes. Configure the application to build the document store on Amazon S3.
Use Amazon Elastic Block Store (Amazon EBS) for the EC2 instance root volumes. Configure the application to build the document store on Amazon S3 Glacier.
Use at least three Provisioned IOPS EBS volumes for EC2 instances. Mount the volumes to the EC2 instances in a RAID 5 configuration.
Explanations:
While regular snapshots of EBS volumes can help with backup and disaster recovery, they do not provide immediate access to documents and do not improve availability in the way required. Additionally, using snapshots across multiple Availability Zones does not inherently provide high availability for the document storage itself.
Amazon S3 is designed for high availability and durability. By configuring the application to use S3 for document storage, the company can ensure that documents are immediately available upon request. S3 automatically handles replication across multiple Availability Zones, thus meeting the high availability requirement.
Amazon S3 Glacier is designed for archival storage and is not suitable for immediate access needs, as it involves retrieval times that can range from minutes to hours. This option would not meet the requirement for documents to be returned immediately when requested.
While using Provisioned IOPS EBS volumes in a RAID 5 configuration can enhance performance and redundancy, it does not provide cross-AZ availability. If one Availability Zone fails, the documents would still be inaccessible, thus not meeting the high availability requirement.
It seems to me that the answer is:
Use Amazon Elastic Block Store (Amazon EBS) for the EC2 instance root volumes. Configure the application to build the document store on Amazon S3.