2012-07-18 SSD speed

I wondered why my SSDs got so slow.
So using hdparm I measured that my OCZ Vertex3 did only 230MB/s. Since it is advertised to do > 500MB/s, this was disappointing.
In a stroke of genius I decided to read the whole SSD (in blocks of 512MB) to see if this decrease is constant.
It is not:

OCZ Vertex3 (2.15):

As you can see, for the range between 15GB and 55GB the speed indeed is 550GB: this range is never written to (not even partionated).
So it looks as if indeed an SSD can do e.g. 550MB/s until it is written to, then the speed sometimes even halves.

OCZ Vertex2 (1.25):

OCZ Vertex2 (3.5 1.22):

Intel 320 SSDSA2CW120G3:

As a comparison I also graphed my regular rotational WDC (1TB) harddisk:

The script to measure this can be downloaded here: measure.sh.
To plot, you can use the following script: plot.sh.