@ bouzane
I always like to help to rid the world of misinformation like this...
"For really old Blu-Ray drives (like 3 years ago). The PS3 uses a fairly compact triple wavelength OPU.
From my own personal experience testing a Sony BD-RE drive (actually uses a Panasonic drive mechanism) and a Hitachi-LG drive of similar specs, for similar sized data sets the BD drive typically has almost the same if not significantly faster random seek times. That's generally because data sets between 4-8GB span the entire disc for for DVD-ROM while only covering a third of a BD-ROM, so on average a BD-ROM is going to have seek times in the range 50-100ms with a worst case scenario of around 200-230ms. The DVD-ROM drive will average between 110-150ms with a worst case scenario of around 170-230ms.
Of course once you start getting into larger data sets that that Blu-Ray can handle the average and worst case scenarios (which is an entire disc sweep which takes around 350-400ms) will eclipse the worst case conditions on a DVD-ROM. That being said, even with 23+GB of data with a 100 randomly generate seek sectors I still get around 100ms on average. Besides, if you find the need to randomly jump around to random sectors greater than 4GB in span, then your title has bigger issues than the capabilities of the drive."
http://forum.beyond3d.com/showthread.php?t=42157&highlight=speed&page=2
"2x Blu-ray Drive (72Mbps(9MB/s))
Single Layer (2http://www.neogaf.com/forum/newreply.php?do=newreply&p=10460097
NeoGAF - Reply to Topicx CLV) - Constant Linear Velocity (Same speed across entire disk)
Double Layer - Couldn't find any data but no games have been released on a double layer yet.
Entire Blu-ray Disk is read at 9MB/s.
12x DVD-Rom Drive SL (9.25MB/S-15.85MB/s(AVG ~8x(10.57MB/s) DL (4.36MB/s-10.57MB/s(AVG ~6x(7.93MB/s)
SL(DVD-5) 12x Max (5-12x Full CAV) - Constant Angular Velocity (Speed Varies from edge to edge)
DL(DVD-9) 8x Max (3.3-8x Full CAV) - Constant Angular Velocity (Speed Varies from edge to edge)
SL DVD is 1.57MB/s > SL Blu-ray
DL DVD is 1.07MB/s < SL Blu-ray
Majority of 360 games are on DVD-9."
http://forum.beyond3d.com/showthread.php?t=42157
Note single layer 360 DVD games are small enough to fit easily on the PS3 harddrive entirely, which of course loads a lot faster than either PS3 Blu-Ray or 360 DVD.
