Dell PowerFlex compression is a feature that operates exclusively on Fine Granularity (FG) storage pools. This makes an FG storage pool a fundamental software-level requirement. At the hardware level, compression requires a high-performance, low-latency write-back cache on each Storage Data Server (SDS) to ingest and stage data before the compression algorithm is applied. This cache must be configured on persistent memory. NVDIMMs are a primary hardware choice for this cache due to their extremely low latency and built-in power-loss protection, which guarantees data integrity for writes held in the cache. A minimum of two NVDIMMs per server is required to provide redundancy for the cache.

1. Dell PowerFlex Product Guide (Version 4.0):

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Section: Compression: "Compression is supported on fine granularity storage pools only. The SDSs that are part of the compressed storage pool must have a write-back cache that is configured on either NVDIMM or NVMe devices." This confirms the requirement for a Fine Granularity pool (Option B) and the use of NVDIMM (Option A) or NVMe for the cache.

2. Dell PowerFlex: Architecture and Design Guide:

Section: Data Layout and Protection

Subsection: Compression and Caching: The guide details that for features like compression

a write-back cache is mandatory to maintain performance. It specifies that this cache resides on very fast

persistent media such as NVDIMM-N or NVMe

with NVDIMM-N often cited for its performance characteristics critical to cache operations.

3. Dell PowerFlex: Best Practices Guide:

Section: Performance Considerations

Subsection: Compression: "For optimal performance with compression

configure the write-back cache on the lowest-latency persistent devices available

such as NVDIMMs. A redundant configuration with at least two cache devices per SDS is required for high availability." This supports the "at least two NVDIMMs" (Option A) requirement for a robust setup.