> > This takes us back to the wonderful world of Logical IOCS vs Physical IOCS. In the > Mainframe world there as always been a diference between Logical I/O (the program's > write of 80 bytes) and the Physical I/O (the writing of a 4K data block to a device > by an operating system). In the PC world where Linux grew up, there has never been > such a divide and it has been handled by device drivers and cache.
At least for disk I/O you DO have "sort of" the same concept available to you: your program calls a "library routine" (aka access method), which passes it to a device driver, which then sends a command to the SCSI controller (psuedo EXCP), which puts a command on the SCSI bus (SIO?). I'm not saying things are equivalent, but there are parallel concepts involved. Later on, the concept of asynch. I/O was surfaced which enables an application programmer to start an I/O and check on the outcome later on. The point is that as things like SCSI controllers get "smarter" and more powerful, then the application and OS developers can take advantage of these features. I know, I know: the XA architecture is 20+ years old, but these guys are catching up, just be patient. :) ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
