6 . 7
S U M M A R Y
109
preallocated blocks in the directory should be trimmed back. BFS trims direc-
tory data when the directory i-node is flushed from memory. This approach
to trimming the preallocated data has several advantages. The preallocation
of data for the directory allows the directory to grow and still remain con-
tiguous. By delaying the trimming of data until the directory is no longer
needed, the file system can be sure that all the contents of the directory are
contiguous and that it is not likely to grow again soon.
6.7
Summary
This chapter discussed the issues involved in choosing where to place data
structures on disk. The physical characteristics of hard disks play a large role
in allocation policies. The ultimate goal of file system allocation policies is
to lay out data structures contiguously and to minimize the need for disk
seeks. Where a file system chooses to place i-nodes, directory data, and file
data can significantly impact the overall performance of the file system.
Practical File System Design:The Be File System
, Dominic Giampaolo
page 109
Summary :
By delaying the trimming of data until the directory is no longer needed, the file system can be sure that all the contents of the directory are contiguous and that it is not likely to grow again soon. Where a file system chooses to place i-nodes, directory data, and file data can significantly impact the overall performance of the file system.
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data,directory,file,system,disk,trimming,structures,policies,grow,allocation,109,place,preallocated