Problem: Designing an Efficient File Storage System

You are tasked with designing a file storage system for a cloud platform. The system must efficiently store and retrieve files of varying sizes while minimizing the storage cost. Here are the requirements:

Constraints:

File Size Distribution: Files vary significantly in size. Some files are small $($a few kilobytes$),$ while others are large $($several gigabytes$).$ The storage system should efficiently manage this wide range of file sizes.

Redundancy and Reliability: To ensure reliability, files must be replicated across multiple data centers. However, the replication factor $($the number of copies$)$ can vary based on the file's priority $($critical files are replicated more than non$-$critical files$).$

Efficient Access: Frequently accessed files $($hot files$)$ should be stored in a way that allows faster access, while less frequently accessed files $($cold files$)$ can be stored in a more cost$-$effective manner.

Version Control: Files can be updated over time, and multiple versions of each file must be maintained. The system should provide efficient ways to store and retrieve different versions of the same file.

Deduplication: The system should avoid storing duplicate files. If multiple users upload the same file $($or slightly different versions of the same file$),$ the system should store only the unique content.

Data Encryption: All files must be stored in an encrypted format to ensure security. The encryption mechanism should not introduce significant overhead when accessing the files.

Objectives:

Design an algorithm or a set of algorithms for:

Storage Allocation: Decide how to allocate storage space for files of different sizes.Replication Strategy: Determine a replication strategy that balances reliability and storage cost.File Versioning: Manage and efficiently retrieve different versions of a file.Deduplication: Implement deduplication in a way that can handle encrypted files.Access Optimization: Optimize access to hot files while minimizing cost for cold files.

Questions:

Storage Allocation Algorithm: Propose a data structure and algorithm to handle the allocation of storage space for files of varying sizes while ensuring minimal fragmentation.

Replication Strategy: Design an algorithm to determine the replication factor based on file priority, and how to efficiently store the replicas in geographically diverse data centers.

Version Control System: How would you manage file versioning to minimize storage space while ensuring fast retrieval of any version? Would you use a full copy for each version, or a delta encoding strategy? Why?

Deduplication with Encryption: Traditional deduplication relies on comparing file contents. However, with encryption, file contents are different even if the original files are the same. Propose a solution to perform deduplication in an encrypted storage system.

File Access Optimization: Suggest a caching mechanism or any other optimization technique to store hot files in a way that allows fast retrieval, while cold files are moved to a cheaper, slower storage tier.

Additional Considerations:

How would your design handle scalability as the number of users and files grows into the millions or billions?

How would you balance between reducing latency for file retrieval and the overall storage cost?