A controller receives a write request.

When a controller generates a hash for an incoming write request and finds that the hash already exists in the hash table, the next step is tocompare the new block to the existing block to confirm they are duplicates.

Why This Matters:

Hash Collision Handling:

Hash functions can sometimes produce the same hash value for different data blocks (a "hash collision"). To ensure data integrity, the system must verify that the new block is identical to the existing block before deduplication occurs.

Data Integrity:

Comparing the blocks ensures that only true duplicates are deduplicated, preventing data corruption or loss due to hash collisions.

Why Not the Other Options?

A. The next incoming block is then hashed to see if it can be deduplicated:

Hashing the next block is unnecessary at this stage. The focus is on verifying whether the current block is a duplicate.

B. Deep level compression is then applied to the newly hashed block:

Compression is a separate process from deduplication and does not occur immediately after hashing.

D. Purity//FA will expand the block to see if it can deduplicate a larger dataset:

Expanding the block is not part of the deduplication process. Deduplication operates on individual blocks, not larger datasets.

Key Points:

Hash Table Lookup:Identifies potential duplicates based on hash values.

Block Comparison:Confirms that the new block matches the existing block to ensure data integrity.

Deduplication:Eliminates redundant data to optimize storage efficiency.

References:

Pure Storage FlashArray Documentation: "Understanding Deduplication in Purity//FA"

Pure Storage Whitepaper: "Data Reduction Techniques in FlashArray"

Pure Storage Knowledge Base: "How Deduplication Works in FlashArray"