IBM Midrange System DS4000 Series Hardware Manual page 545

C
Solid State Drives on the IBM
Appendix C.
System Storage DS5000 series
In this section, we discuss Solid State Drives (SSD), which is a new feature of the IBM
System Storage DS series that was introduced with the DS5000 storage subsystems. We
compare this technology to hard disk drives (HDD), and we base this comparison on tests we
ran that compared SSDs to HDDs. Lab tests show a significant performance advantage with
SSDs with a substantial reduction in the number of drives needed to meet the desired level of
performance. Fewer drives translate into a smaller physical footprint, reduced energy
consumption, and less hardware to maintain. Tests also showed better application response
times using SSDs, which leads to increased productivity and higher customer satisfaction.
SSD technology was introduced more than two decades ago. Until recently, however, the high
cost-per-gigabyte and limited capacity of SSDs restricted deployment of these drives to niche
markets or military applications. Recent advances in SSD technology and economies of scale
have driven down their cost, making them a viable storage option for many I/O intensive
enterprise applications. While the cost of SSDs is trending downward, the dollar per gigabyte
cost for SSDs is still substantially higher than that of HDDs. It is not cost-effective or
necessary to replace all HDDs with SSDs. For example, infrequently accessed (cold) data
can reside on lower cost HDDs, and frequently accessed (hot) data can be moved to SSDs
for maximum performance. The appropriate mix of SSDs and HDDs can be used to strike a
proper balance between performance and cost.
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