hfs_ra_per_disk(5)

VALUES

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 specifies the amount of read-ahead permitted per disk drive.

The total amount of read-ahead is determined by multiplying hfs_ra_per_disk by the number of drives in the logical volume. If the file system does not reside in a logical volume, then the number of drives is effectively one.

The total number of read-ahead blocks that the kernel may have outstanding for a single HFS file system is constrained by hfs_max_ra_blocks.

hfs_ra_per_disk and hfs_max_ra_blocks should be adjusted according to the characteristics of the workload on the system.

For more information, see the examples in the description of hfs_max_ra_blocks(5).

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_ra_per_disk was developed by HP.

SEE ALSO

hfs_max_ra_blocks(5), hfs_max_revra_blocks(5), hfs_ra_per_disk(5), hfs_revra_per_disk(5), vxfs_max_ra_kbytes(5), vxfs_ra_per_disk(5)