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Global memory is a crucial component in the architecture. All read and write operations are transferred to and from global memory. Transfers between the host processor and channel directors can be processed at much greater speeds than transfers involved with hard drives. PowerMaxOS uses complex statistical prefetch algorithms which can adjust to proximate conditions on the array. Intelligent algorithms adjust to the workload by constantly monitoring, evaluating, and optimizing cache decisions.
PowerMax arrays can have up to 2 TB of mirrored DDR4 memory per engine and up to 16 TB mirrored per array. Global memory within an engine is accessible by any director within the array.
Dual-write technology is maintained by the array. Front-end writes are acknowledged when the data is written to mirrored locations in the cache. In the event of a director or memory failure, the data continues to be available from the redundant copy. If an array has a single engine, physical memory mirrored pairs are internal to the engine. Physical memory is paired across engines in multi-engine PowerMax 8000 arrays.
PowerMaxOS can correct single-bit errors and report an error code once the single-bit errors reach a predefined threshold. To protect against possible future multi-bit errors, if single-bit error rates exceed a predefined threshold, the physical memory module is marked for replacement. When a multi-bit error occurs, PowerMaxOS initiates director failover and calls out the appropriate memory module for replacement.
When a memory module needs to be replaced, the array notifies Dell Support, and a replacement is ordered. The failed module is then sent back to Dell Support for failure analysis.