SUPPLEMENT SSD
is storage tiering. This type of solution leverages multiple types of storage media with different capacities and performance capabilities. Intelligent tiering software will dynamically move data between the various storage media volumes making up the total pool of storage. This allows the most actively accessed data to be stored on the highest performing solid state media, while less frequently accessed data is allocated to the most cost-effective disk volumes.
Both caching and tiering solutions can be deployed in a number of ways and at various levels of the host server and storage subsystem hierarchy. An added benefit of placing Solid State Storage in or directly attached to the server, whether on a PCI-e card or SSD form factor, is that it further reduces storage latency. For the fastest possible performance, it is important to keep storage resources as close to the server processors as possible. The further they are from the server, the more time it takes to move I/O requests back and forth.
Using Solid State Storage as a cache or tiered approach Most storage system deployments generally over-allocate storage to anticipate data capacity planning requirements. With this in mind, Solid State Storage costs and limited capacity (when compared to traditional rotating media) make complete replacement of spinning media cost prohibitive to all but the least cost sensitive application deployments.
The approach of using Solid State Storage as a cache or as a tiered level of storage is a cost-effective solution because it only requires enough Solid State Storage capacity to store and accelerate the most frequently accessed application data. However, when access to all application data is considered mission-critical or when the highest possible performance enhancement is required, then storing all the application data on a dedicated Solid State Storage device is the right approach.
SSD8
www.snseurope.info I October/November 2011
An unexpected side benefit of these Solid State Storage approaches is that the performance of the associated spinning HDD volumes in the system are also enhanced because a majority of the workload normally serviced by the HDDs is now offloaded to the Solid State Storage. In some environments there is sufficient shift in application performance critical data accesses to Solid State Storage allowing replacement of the more expensive high performance HDDs with more cost-effective near line HDDs.
Protecting data
No matter which approach is deployed, data stored on Solid State Storage still needs to be protected and actively monitored. While it is true that Solid State Storage removes most of the mechanical elements that make HDDs more susceptible to failures over time, it is important to remember that Solid State Storage can fail and will eventually wear out due to write endurance limitations. User data can be protected against SSD drive failure by utilising high-availability RAID algorithms and software features. Technology such as LSI MegaRAID SSD Guard™ preserves data availability by automatically copying data from an SSD, with a detected performance
or reliability issue, to a designated spare or newly inserted drive.
When not to invest in Solid State Storage
Solid State Storage undoubtedly delivers cost-effective application performance enhancement when applied to transactional random access workloads and especially when data is accessed frequently or repetitively. As an example, a database application that randomly and frequently accesses active portions of the larger database is an excellent way to apply Solid State Storage to accelerate application performance. However, application data that is accessed infrequently or isn’t performance- critical is still best stored on traditional higher capacity and lower cost spinning HDDs. For example, a large amount of sequentially read data may not benefit from being cached in Solid State Storage unless portions of the data are re-read multiple times and the majority of those portions of read data fits within the available Solid State Storage capacity.
For more information on LSI Solid State Storage solutions, visit:
http://www.lsi.com/ solutions/Pages/
SolidState.aspx
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