The Cache Value of SSD

When I speak with IT Managers about Solid State Disk (SSD) one of the most common questions is how and where should it be implemented? There are many options but an extremely simple risk free way to get started is using SSD as a large cache in front of a disk array.Most disk arrays or RAID controllers have some cache on them already to help with performance, but in comparison to SSD these are relatively small. With SSD the memory available to cache can expand to 64GB or more. This makes the likelihood of a cache miss significantly lower. Also Flash SSD, which now dominates the market, is best suited for read heavy operations which in most cases a cache is. Using SSD as a cache first is also ideal for the risk adverse. Since all the data eventually lands back on the mechanical drive based array there is limited concern over what to do if the SSD fails.

The big advantage to using SSD as cache is that there is limited if any changes that need to be made to the application or the processes that protect that application. When SSD is used as a stand alone tier, care must be taken to make sure the application knows how to use that tier and changes or additions need to be made to the data protection process so that data on the SSD tier is protected. SSD cache is managed by the controller or caching device, the application and associated protection processes function normally.

SSD cache implementations can come in several forms. There are array controllers that have changed their controller software to support an SSD device and there are stand alone caching appliances designed to sit in front of NAS or SAN based mechanical drive based arrays. All have their role to play and we will explore them in more detail in our next entry. For more information on SSD, please see our SSD resources page.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.