Ph.D. in Computer Science at Rutgers University

File System

In Computer Architecture catalog, I posted Memory Hierarchy series, and talked about hardware structure of Disk. This post will discuss more on I/O in operating system level. First of all, I'll discuss on RAID, then interrupt and DMA.

I/O basic concept

I/O, abbreviation for Input/Output, is an important part for modern Von Neumman Architecture. We know memory is like a hierarchical structure, the faster the access speed, the smaller the capacity and the higher the cost. External storage (Disk/Tape) enables a computer to store data when power is off. However to access Disk is slow because the data has to go through ICH (I/O Controller Hub), previous known as South Bridge Chipset via DMI bus (5 GB/s in DMI 2.0 and 8 GB/s in DMI 3.0). Compared to access disk, access RAM is much more faster because RAM is connected to CPU directly via Memory Bus (12.8 GB/s for 1600mhz DDR3 RAM).


The two pictures above shows the architecture for Intel Nehalem and Skylake. Nehalem encapsulate memory controller inside CPU, and from then, IOH (also known as North Bridge Chipset) is evicted and everything was in IOH is now in CPU; So we don't see IOH in Skylake.