220 The Green and Virtual Data Center
For example, NFS filer data access can be boosted using caching I/O accel-
erator appliances or adapter cards.
More SSDs are not in use because of the perceived cost. The thought
has been that SSDs in general costs too much compared to HDDs. When
compared strictly on a cost per gigbyte or terabyte basis, HDDs are cheaper.
However, if compared on the ability to process I/Os and the number of
HDDs, interfaces, controllers, and enclosures necessary to achieve the same
level of IOPS or bandwidth or transaction or useful work, then SSDs may
be more cost-effective for a given capacity. The downside to RAM com-
pared to HDD is that electrical power is needed to preserve data.
RAM SSDs have, over the years, addressed data ...