The PowerMax storage array uses a strategy that is targeted to provide the best data reduction without compromising performance. The PowerMax Adaptive Compression Engine (ACE) combines these attributes:
- Hardware acceleration – Each PowerMax engine is configured with two hardware compression modules (one per director) that handle data compression and decompression. These hardware modules are also capable of generating Hash IDs that enable deduplication and are more powerful than the modules used with VMAX All Flash arrays.
- Optimized data placement – Based on compressibility, the data is allocated in different compression pools that provide a compression ratio (CR) from 1:1 (128 KB pool) up to 16:1 (8 KB pool) and are spread across the PowerMax back end for best performance. The pools are dynamically added or deleted based on need.
- Activity Based Compression (ABC) – Typically, the most recent data is the most active, creating an “access skew.” ABC relies on that skew to prevent constant compression and decompression of data extents that are frequently accessed. The ABC function marks the busiest 20 percent of all allocated data extents in the system, and skips the compression workflow for those extents. Data extents that are highly active remain uncompressed, even if their storage group has compression enabled. As the data extents become less active, they are automatically compressed while newly active extents are part of the “hottest” 20 percent (if enough free storage capacity is available).
- Fine grain data packing – When PowerMax compresses data, each 128 K track is split into four 32 K buffers. All buffers are compressed in parallel. The total of the four buffers results in the final compressed size and determines in which compression pool the data is allocated. Included in this process is a zero reclaim function that prevents the allocation of buffers with all zeros and no actual data. For a small size read or write, only the necessary buffers participate, not all four.
- Extended data compression (EDC) – Data that is already compressed automatically goes through additional, more powerful compression if it remains untouched for over 30 days, increasing storage efficiency even more.
Additionally, note the following:
- Compression is enabled or disabled at a storage group level for ease of management. Generally, most databases can benefit from storage compression. Customers might decide not to enable compression if the data is fully encrypted or if the storage group contains data that is continuously overwritten.
- When compression is enabled, all new writes benefit from inline compression. If the storage group already contains data when compression is enabled, it goes through background compression with low priority (relative to application I/Os).
In addition to more powerful hardware compression modules, the PowerMax storage array also introduces data deduplication (dedupe) capability. PowerMax deduplication is automatically enabled or disabled when compression is enabled or disabled (compression and deduplication cannot be managed separately).
For more information about the PowerMax Adaptive Compression Engine, see Data Reduction with Dell EMC PowerMax.