Organization: Schlumberger Laboratory for Computer Science
Lines: 13
Nntp-Posting-Host: bandit
A number of microprocessor based OSs had "extent-based" filesystems,
if you mean one in which files were allocated as a group of sequential
chunks of disk space. The vintage 73 Datapoint 5500 (if I remember right)
had it, and its apparant conceptual son, Motorola's floppy-disk only MDOS.
For SDOS (an OS for Motorola 6800s), I personally implemented a file system which allocated extents of clusters (fixed size chunks of contiguous blocks), recorded every cluster allocated in a file "header cluster" (gauranteed 2-seek worst case random access for arbitrarily large files). For open files, the file system would dynamically recover the extents when accessing the file to optimize sequential reads; often, this also reduced random access to single seeks.
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Ira Baxter email: baxter@slcs.slb.com ph: 1-512-331-3714
Schlumberger Laboratory for Computer Science
8311 North RR 620 [for snail mail, use PO Box 200015 instead]
