Deduplication and Compression Techniques in All‑Flash Arrays: Implementation Details and Vendor Comparisons
All‑flash storage arrays increasingly rely on deduplication combined with compression to extend SSD lifespan, and this article explains the underlying block‑level workflow, hash‑based fingerprinting, and key implementation differences among vendors such as EMC Xtremio, Pure Storage, and HP 3PAR.
Deduplication and compression have become essential features in all‑flash storage arrays because they reduce the amount of data written to SSDs, thereby extending the devices’ limited write‑life and protecting investment.
In EMC’s Xtremio implementation, host data is first divided into fixed‑size 8 KB blocks, each block’s fingerprint is calculated with a strong SHA‑1 hash, and the fingerprint is distributed across nodes for deduplication; new blocks are stored while duplicate blocks increase a reference count.
The receiving node writes the data to a cache, compresses it, and when the cache reaches a flush threshold, the compressed data is written to the appropriate storage location based on the fingerprint distribution. Xtremio’s deduplication is performed before compression, uses strong hashing, places deduped data directly on individual disks without a global mapping layer, and relies on each disk’s own garbage‑collection instead of a global GC process.
The article also compares other vendors. All‑flash systems implement online deduplication (including compression) to avoid extra write cycles that would occur with offline processing. Block sizes vary: Xtremio moved from 4 KB to 8 KB, Pure Storage advertises variable block sizes from 512 B to 32 KB (in multiples of 4 KB), and HP 3PAR uses 16 KB blocks.
Metadata handling differs: Xtremio uses a two‑stage metadata scheme (LBA‑to‑fingerprint and fingerprint‑to‑physical‑block address), while Pure Storage and HP 3PAR employ a weaker hash followed by byte‑by‑byte comparison to confirm duplicates.
Regarding scalability, Xtremio supports scale‑out with dual‑controller clusters up to 16 controllers and provides global deduplication, whereas Pure Storage focuses on scale‑up without scale‑out capability.
Some vendors (HP 3PAR, Skyera) accelerate deduplication and byte‑wise comparison using dedicated ASICs or accelerator cards.
Because all‑flash arrays perform online deduplication and compression, the incompatibilities that existed with offline deduplication in traditional disk arrays no longer apply.
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