HistoVAMDoc.tioga
Hauser, May 13, 1985 1:08:28 pm PDT
HistoVAM
CEDARCHEST 6.0 — FOR INTERNAL XEROX USE ONLY
HistoVAM Documentation
Carl Hauser
© Copyright 1985 Xerox Corporation. All rights reserved.
Abstract: A hack to analyze the distribution of free run sizes on a logical volume.
Created by: Carl Hauser
Maintained by: Carl Hauser <Hauser.pa>
Keywords: VAM, Volume Allocation Map, VM
XEROX Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, California 94304
For Internal Xerox Use Only
1. Usage
HistoVAM -- show the VAM for the "system" volume
HistoVAM volumeName -- show the VAM for the named volume (e.g., Debugger)
2. Known bugs
The program looks for adjacent 16 adjacent blocks which are either all free or all allocated. If a set of 16 blocks is neither all free nor all allocated, it is counted as "Mixed". The number of mixed 16-block runs is shown in the first line of the resulting output. Since the mixed blocks are not further analyzed, the number of free blocks occuring in mixed 16-block runs is, to first order of approximation, 8 times the number of mixed 16-block runs.
As a further result of not looking inside mixed 16-block runs, the program may underestimate the length of a free run by up to 30 blocks.