"It's a fairly well known fact that solid state disk (SSD)
performance can suffer over time. This was quite common in early
SSDs, but newer controllers have helped reduce this problem through
a variety of techniques. In part one of this two-part look at SSDs,
we examine the origins of the performance problem and some
"SSDs and Performance
"Performance degradation problems are a result of how SSDs are
constructed and how file systems and applications interact with
them. Almost all of the problems stem from the design of SSDs.
"In my last article, I presented the basic concepts for
constructing an SSD. When SSDs are written to (programmed), they
are written in units of pages (typically 4KB). But SSDs are erased
in units of blocks, which are much larger than pages (the previous
article used an example where the block size was 128 pages or
512KB). This difference in units for writing and erasing is a key
to understanding why SSD performance can degrade over time."