The PowerMax storage system uses a strategy that is targeted to provide optimal data reduction without compromising performance. The PowerMax Adaptive Compression Engine (ACE) is the combination of the following components:
- 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—The application’s data is stored in different compression pools that provide a compression ratio (CR) from 1:1 (128 KB pool) up to to 16:1 (8 KB pool) and is 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 allows them to skip the compression workflow. Data extents that are highly active remain uncompressed, even if compression is enabled for their storage group. As the data extents become less active, they are automatically compressed while newly active extents become part of the “hottest” 20 percent (as long as enough free storage capacity is available).
- Fine-Grain Data Packing—When PowerMax compresses data, each 128 KB track is split into four 32 KB 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 write or read, only the necessary buffers participate, not all four buffers.
- Extended Data Compression (EDC)—Data that is already compressed automatically goes through additional, more powerful compression if it is untouched for over 30 days, increasing storage efficiency.
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 database is fully encrypted or if a storage group contains data that is continuously overwritten (such as Oracle redo logs).
- 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 (as compared to application I/Os, which get higher priority).
In addition to providing more powerful hardware compression modules, the PowerMax storage system also allows data deduplication (dedupe). PowerMax deduplication is automatically enabled or disabled when compression is enabled or disabled (compression and deduplication cannot be managed separately).
PowerMax deduplication operates at 128 KB granularity. Because Oracle ASM Allocation Units (AU) have a granularity of 1 MB or larger, PowerMax deduplication works well with Oracle databases residing in ASM disk groups. Any new ASM extent is aligned at 1 MB (or higher) offsets, allowing the PowerMax storage system to easily determine if the data is unique, without misalignment concerns. As shown later in this white paper, the PowerMax storage system achieves 100 percent deduplication benefits for Oracle databases residing in ASM.
For more information about PowerMax data reduction, see this white paper: