IN SAME CONDITION, HOW THIS HAPPEN,or something is wrong with “A7B2”
thank for answer?
The WD5000AAKS-00A7B2 appears to be an older model with two 250GB platters, whereas the WD5000AAKS-00V1A0 has a single 500GB platter.
The spread of data points for the access time graph (~8msec) would suggest that both are 7200 RPM drives.
The large difference in the data transfer rate is due to the increased data density of the newer drive. AFAIK, the transfer rate increases as the square root of the data density, so we would expect that the older drive would have a density of …
500 x (94.5 / 135.4)^2 = 244GB per platter
This confirms that it has two 250GB platters. If you compare the DCMs on the label, you will probably find a difference in the media type.
See these threads for a similar discussion, with more info:
http://community.wdc.com/t5/Desktop/WD6402AAEX-new-drive-slower-than-older-drive/m-p/39315#M2116
http://community.wdc.com/t5/Desktop/Check-hard-disk-motor-speed/m-p/39279#M2114
