How Srm And Hfs Directories And Files Are Stored - HP 9000 200 Series Manual

How SRM and HFS Directories and Files Are Stored
To most efficiently use disc space, the SRM system and HFS system store files non-
contiguously and add space allocations to files as needed.
Non-Contiguous Storage of SRM and HFS Files
To avoid wasting disc space, SRM and HFS may "fragment" a file to fill unused disc
sectors. This process is transparent and cannot be externally controlled. By "filling the
gaps" automatically, the system eliminates the need to pack the shared disc's files.
Space Allocation for SRM and HFS Directories and Files
SRM and HFS files and directories grow dynamically as data is entered into them.
This type of file is called extensible, because its size may be automatically extended
(by BASIC) whenever it would otherwise overflow. (For SRM, the amount of space
added to the
file~s
current size is known as the "extent size" of the file; this amount of
space is the same as the amount of space that was originally allocated to the file when
it was initially created.)
Rather than restricting a file's space to that allocated when the file is created (for
example, with a CREATE statement), the system determines disc space requirements
when data is sent to the file (for example, by an OUTPUT statement). If additional
data placed into a file would cause the file to overflow its current space allocation, the
system automatically allocates more space for the file.
Similarly, directories grow only as entries are added. As a file or directory is created,
another record is added to the containing directory.
Files are extended as long as there is sufficient unused disc space on the same volume.
Excess data from a file will not be placed on any other volume, however.
5-12
Using
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