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Summary: 39
The Fast File System
When UNIX was first introduced, the UNIX wizard himself Ken
Thompson wrote the first file system. We will call that the "old
UNIX file system", and it was really simple. Basically, it looked
like this on the disk:
Super block | Inodes | Data blocks
The super block contained information about the entire file
system: how big the volume is, how many inodes there are, a
pointer to the head of the free list of blocks, and so forth. The
inode region of the disk contained all the inodes for the file sys-
tem. Finally, most of the disk was taken up by data blocks.
The good thing about the old file system was that it was sim-
ple, and supported the basic abstractions the file system was
trying to deliver: files and the directory hierarchy.
39.1 The Problem: Poor Performance
The problem: performance was terrible. As measured by
Kirk McKusick and his colleagues at Berkeley [MJLF84], per-
formance started off bad and got worse over time, to the point
where the file system was delivering only 2% of overall disk
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