HP SmartCache technology

Technical white paper | HP SmartCache
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Why caching?
So you may ask, if SSDs are superior in performance, why not use HP IO Accelerators and SSDs in all server configurations?
The answer is that you need to weigh requirements for capacity and performance against the increased costs for those
abilities. As the cost of SSDs is trending downward, SSD technology is making inroads into the enterprise server market to
address the low latency requirements for certain applications. However, even with the performance benefit and lower cost,
SSD technology will not replace HDD technology in the near future since HDDs remain an economical and durable (long-
term) storage medium. Also, SSDs support a finite number of write cycles before they begin to degrade, although their
durability is improving and the capacity is increasing to where SSDs are more viable for enterprise applications.
Using a high performing all-SSD configuration for an application may be viable for applications with modest capacity
requirements. Still, it is difficult to ignore HDDs for their high capacity and greater durability at a very economical price,
particularly in enterprise systems that may require thousands of storage devices.
HP SmartCache technology eases your decisions by providing an incremental, economical way to introduce SSD technology
into your environment. HP SmartCache provides SSD performance benefits while simultaneously preserving investments in
previously purchased hard disk assets.
How does caching work?
Caching works by intelligently placing data in a lower latency device so that responses to future requests for that data can
occur much quicker. If an application requests data that is in the cache (called a “cache hit”) then the lower latency device
can service that transaction. Otherwise, a “cache miss” occurs and the data must be accessed from the original, slower
device. As more cache hits occur, overall performance improves.
Caches are very common in computers. Processors use faster memory caches to speed up instruction execution as they
fetch data from memory DIMMs. HDDs contain caches (also known as buffers) that allow data to be queued to and from the
magnetic media. Host operating systems utilize caches to improve application performance. Caching has proven itself in
many areas of computing because of the nature of how applications access data. Caching improves performance while
maintaining a cost-effective platform. As storage capacities continue to expand, SSDs bring caching to storage systems to
provide a cost-effective performance boost, especially to server configurations.
HP SmartCache architecture
HP SmartCache combines different technologies and device types to close the cost/performance gap. SmartCache uses a
caching architecture where a copy of the data resides on the hard disk drive as well as on a lower latency device that is used
for caching. The basic HP SmartCache architecture is comprised of the following three elements:
• Bulk storage: The first element is the bulk storage device, which can be either HDDs or connections to SAN storage.
• Accelerator: The second element, the accelerator, is a faster/lower latency device that caches data. The capacity of the
accelerator is less than the capacity of the bulk storage device.
• Metadata: The final element is metadata, information held in a relatively small storage area that maps the location of
information residing on the accelerator and bulk storage devices.
The HP SmartCache architecture is flexible and supports numerous device types for bulk storage, accelerator, and
metadata. The HP SmartCache architecture can adapt to accommodate the evolution of storage devices. Initially available
HP SmartCache solutions are designed for DAS and SAN systems.