Cache and CPU Power

Unique Cache Architecture

Unlike any other storage system, the system's design embeds the read/write cache into the same hardware module as the disks. This has distinct advantages:

• Distributed cache. The cache is implemented as a distributed cache, so that all cache units can concurrently serve host I/O and perform cache-to-disk I/O. This ensures that the cache will never become a bottle-neck.
• High cache-to-disk bandwidth. Aggressive pre-fetching is enabled by the fact that cache-to-disk bandwidth is the internal bandwidth of a module. Implemented over two PCI-X buses, a module thus provides dozens of gigabytes per second for the whole system.
• Powerful cache management. The unique design enables the system to read a large cache slot per disk read, while managing least-recently-used statistics in small cache slots. This dual capability is made possible by the combination of the system's huge processing power and high cache-to-disk bandwidth.

Massive CPU Power

The fact that each data module has its own processing power provides the XIV system with dozens of powerful CPUs. This power is used for sophisticated caching algorithms, support for small cache slots, snapshot performance, and so on. IBM XIV also offers dual processors in its interface modules, enabling up to a 30% increase in performance, depending on workload.

The massive CPU power ensures high performance through higher cache hit rates and smaller snapshot overhead.