NAME
hfs_max_ra_blocks — maximum number of read-ahead blocks that kernel may have outstanding for a single HFS file system
VALUES
Default
8
Specify an integer value or use an integer formula expression.
DESCRIPTION
When data is read from a disk drive, the system may read additional data
beyond that requested by the operation.
This "read-ahead" speeds up sequential disk accesses
by anticipating that additional data will be read and
having it available in system buffers before it is requested.
This parameter limits the number of read-ahead blocks that the kernel
is allowed to have outstanding for any given HFS file system.
The limit applies to each individual HFS file system,
not
to the system-wide total.
hfs_max_ra_blocks
and
hfs_ra_per_disk
should be adjusted according to the characteristics of the workload on
the system.
To determine the block size of the file system containing the
current directory, use the command:
df-g.
EXAMPLES
A software development environment typically consists of small or
medium sized I/Os with a fair number of disk seeks.
Therefore,
hfs_max_ra_blocks
should be set to 8-to-16 blocks and
hfs_ra_per_disk
should be set to 32-to-64 kilobytes.
An out-of-core solver for an MCAE application has a significant sequential
I/O component, so
hfs_max_ra_blocks
should be set to 64-to-128 blocks and
hfs_ra_per_disk
to 128-to-256 kilobytes.
WARNINGS
All HP-UX kernel tunable parameters are release specific.
This parameter may be removed or have its meaning changed in
future releases of HP-UX.
AUTHOR
hfs_max_ra_blocks
was developed by HP.
Printable version
