Vendors say they're the same...
and now there are dedicated with SAS and others with SCSI

I've worked with scsi servers, and they go damn fast serving webs...

SAS will do the same?

Anyone has performance difference with those 2 hard drive types ?

thank you

They are pretty much the same thing. SAS drives are essentially just notebook drives (2.5") with a SCSI or SATA interface. We've built a few servers with them and I was actually impressed by their performance.

What about the 3.5" SAS drives vs. 3.5" SCSI drives? Same performance?

SAS are SCSI drives with a Serial (SATA) interface and can be 2.5" or 3.5". Unlike SATA, SAS drives uses SCSI commands. But since they're not parallel, they can achieve theoretically higher performance and there' other factors increasing overall performance.

http://en.wikipedia.org/wiki/Serial_Attached_SCSI