In IBM XIV Storage Systems, what design choice helps ensure that the cache does not become a performance bottleneck?

Introduction / Context:
This question evaluates understanding of IBM XIV Storage System architecture. XIV uses a grid of modules, each with processing power, cache, and access to a portion of the storage. The way cache is organized across modules affects overall throughput and scalability. Avoiding a single central cache bottleneck is crucial for large, parallel workloads.

Given Data / Assumptions:

The storage platform is IBM XIV, which uses a grid based design.

Data is distributed across multiple modules in the grid.

The system needs to scale without introducing a single cache bottleneck.

Each option represents a possible cache coordination strategy.

Concept / Approach:
In a scalable grid architecture, responsibility for caching is typically distributed. If each module caches data that it owns or serves, requests can be satisfied locally without constant coordination with a central cache manager. This reduces contention and lock overhead. In contrast, a central cache or strict global tracking of every cached block can create scalability limits as the system grows.

Step-by-Step Solution:
1. Consider how a centralized cache design would behave as the number of modules and requests increases. Central locking or metadata would become a choke point. 2. Recognize that option C describes a fully distributed caching model where each module caches its own data. 3. Option A suggests a central cache locking mechanism that could serialize many operations. 4. Option B mentions industry standard chips, which do not in themselves address bottlenecks. 5. Option D proposes that all modules must understand all cached data at all times, which increases overhead and complexity.

Verification / Alternative check:
IBM architectural overviews emphasize that XIV uses a uniform grid where each module is an independent building block, including caching responsibility for its portion of data. This design supports linear performance scaling when more modules are added.

Why Other Options Are Wrong:
A central locking mechanism tends to limit parallelism and may become a single point of contention.
Using standard chips is an implementation detail and does not guarantee absence of a cache bottleneck.
Tracking all cached data from all modules in every module increases metadata traffic and can itself become a bottleneck.

Common Pitfalls:
Students sometimes focus too much on hardware specification rather than architecture. Another pitfall is assuming strong central control always improves consistency, ignoring the performance penalty. In grid storage systems, distribution of responsibilities is usually the key to scalability.

Final Answer:
The XIV cache avoids being a bottleneck by having each module be responsible for caching the data that resides in that module.