Erasure Coding (EC-X) is an efficient method to save storage space, particularly for data that is infrequently accessed. Given the characteristics of the VM, such as generating large, sequential writes, needing long-term data retention, and infrequent access, post-process compression is the most suitable feature.

Large Sequential Writes: Post-process compression is well-suited for large, sequential writes because it can significantly reduce the storage footprint after the data has been written to disk. It is more efficient for sequential data patterns compared to inline compression, which might add latency during write operations.

Long-term Data Retention: Since the data needs to be stored for years and is only accessed occasionally, post-process compression can help save storage space over time without impacting the performance of current write operations. This method compresses data after it has been written to storage, optimizing storage usage for long-term retention.

Infrequent Access: Data that is rarely accessed benefits from post-process compression because the slight delay in accessing compressed data is acceptable compared to the significant storage savings.

Comparison with Other Options:

Inline Compression: This compresses data as it is written, which can add latency and is less efficient for large, sequential writes.

Flash Mode: This option is intended for performance optimization by pinning data in the flash tier, which is not relevant for space saving.

Cache Dedup: This reduces the footprint of redundant data in the cache, which is not directly relevant to long-term storage optimization.

Post-process compression aligns well with the characteristics and requirements of the VM described, providing optimal storage efficiency for large, sequential writes and long-term data retention.

References:

Nutanix Bible, Section on Data Reduction Techniques, particularly the comparison between inline and post-process compression​​.

Nutanix-NDB-User-Guide, Guidelines on data storage optimization​​.