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With business growth comes the inevitable hurdle of how to deal with an increased demand for data. The need to increase application and information system responsiveness becomes more apparent as an organisation grows in size. This growth increases the data appetite of mission-critical applications. Storage caching, tiering and tuning techniques enable extending and enhancing the capabilities of SAS, NearLine-SAS and SSD storage devices. These improvements allow administrators to maximise system performance by intelligently and autonomously combining multiple storage device types and leveraging their storage management features. Each of the functions mentioned - storage caching, tiering and tuning - have a unique role to play. The combination is powerful but the individual capabilities are valuable in their own right. Businesses should be relying on these multiple technologies to drive price/performance, improve data availability and keep data safe as they grow.

CACHING FOR PERFORMANCE
Caching allows storage system controllers to use SSD or flash technology to extend its on-board cache, also known as Level 2 (L2) cache. I/O requests are usually serviced from primary Level 1 (L1) cache, but if the request rate is too high, the primary cache may be fully consumed. Caching's goal is to increase I/O by increasing the cache hit ratio. The storage system identifies frequently accessed data, sometimes called "hot data", based on MFU/MRU algorithms (Most Frequently Used /Most Recently Used). As I/O patterns change over time, storage systems monitor and record the patterns to automatically align storage resources to workflow requirements.

Hot data may be small (i.e. 3-5%) compared with total system storage capacity, but it may represent as much as 50-60% of all I/O activity. I/O intensity is why L2 cache is so valuable. By using a secondary cache, a very large proportion of I/O can be serviced from cache; thereby greatly reducing the time required to access data compared to traditional spinning hard drives. If the storage system determines using the extended cache would maximise I/O performance, it migrates data onto L2 cache without the need for intervention by the administrator. The storage system updates its understanding of I/O demand by continuously monitoring I/O patterns.

There are significant benefits to using advanced caching functions, particularly for dynamic environments like virtualised servers and for applications requiring low latency because I/O patterns can change dramatically even within a single workday. Caching has been shown to increase I/O performance by up to 800% depending on the application.

CACHING IS NOT EASY
Effective caching requires evaluating multiple, intersecting factors. Consider, for example, the level of Input/Output Operations Per Second (IOPS). To work effectively for an organisation, a caching feature should automatically measure every transaction and the level of IOPS per data transaction. Every business knows the value of maintaining performance when it comes to customer satisfaction. In today's "always on" connected world, providing reliable service and meeting the expected service levels is everything. Being able to keep performance levels high, even in the face of congestion or a hardware failure, is key.

Automatic caching can also help maintain good performance during hardware failures. Usually an enterprise-class storage system includes two controllers in active/active mode. If one controller fails, the other takes over. The surviving controller must cope with twice the traffic until the failed hardware is replaced, and in the absence of some form of automatic caching, users will likely experience performance degradation. In a storage solution containing a secondary L2 cache, performance degradation is minimised and up to 80% of I/O performance can be maintained.

TIERING FOR EFFICIENCY
In today's enterprise it is critical for data to be properly provisioned to maximise performance and keep price/performance as low as possible. Tiered storage enables allocating data assets in the most optimum manner, which requires simultaneously accounting for efficiency, I/O performance, data protection and uptime. Advanced storage systems currently on the market will support simultaneous use of high performance SAS, Nearline SAS and SSDs. They can automatically provision storage and ensure the provisioning is consistent with corporate policies. Storage tiering is complementary to caching. Unlike caching, tiering uses solid-state memory as permanent storage. Caching is used to dynamically redirect read and write requests.

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