How Dropbox was designed

Internal data storage (Magic Pocket)

Dropbox stores files in chunks of 4MB size and immutable block storage system

Every block is compressed and encrypted. Each block needs a key or name, in which most of the cases is a SHA-256 hash of the block.

Combination of blocks is called Bucket, Combination of Buckets is called Volumes

Each bucket can be replicated across machines or written as erasure coded form

To summarize: A block, identified by its hash, gets written to a bucket. Each bucket is stored in a volume across multiple machines, in either replicated or erasure coded form.

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