在说ext2物理结构之前，要先认祖归宗。
首先，大部分现代文件系统的祖先都能追溯到BSD FFS（Fast File System 1983年 BSD 4.2版本），所以对文件系统的介绍不可能忽略它。从40年后今天来看，BSD FFS的设计理念还有很多值得学习的地方，对于现代文件系统可以说是产生的深远的影响。在它的设计框架里，有一个超级块，一个块位图，一个inode位图和一些预分配的inode表。这种设计可在许多现代文件系统里找到影子。
继续阅读“03 ext2文件系统物理结构剖析”4.2BSD (August 1983) would take over two years to implement and contained several major overhauls. Before its official release came three intermediate versions: 4.1a from April 1982[13] incorporated a modified version of BBN’s preliminary TCP/IP implementation; 4.1b from June 1982 included the new Berkeley Fast File System, implemented by Marshall Kirk McKusick; and 4.1c in April 1983 was an interim release during the last few months of 4.2BSD’s development. Back at Bell Labs, 4.1cBSD became the basis of the 8th Edition of Research Unix, and a commercially supported version was available from mt Xinu.
From: History of the Berkeley Software Distribution – Wikipedia