HP-UX HB v13.00 Ch-14 - JFS

HP-UX Handbook – Rev 13.00 Page 20 (of 47)
Chapter 14 Journaled File System (JFS)
October 29, 2013
usage has limitations depending on how the space within an HSM-controlled file is managed.
NOTE: It is advisable to use hsm_write_ prealloc only when recommended by the HSM
application controlling the file system.
max_seqio_extent_size
Changes the default initial extent size. VxFS determines, based on the first write to a new file,
the size of the first extent to be allocated to the file. Normally the first extent is the smallest
power of 2 that is larger than the size of the first write. If that power of 2 is less than 8K, the first
extent allocated is 8K. After the initial extent, the file system increases the size of subsequent
extents with each allocation.
initial_extent_size
Since most applications write to files using a buffer size of 8K or less, the increasing extents start
doubling from a small initial extent. initial_extent_size can change the default initial extent size
to be larger, so the doubling policy starts from a much larger initial size and the file system does
not allocate a set of small extents at the start of file.
Use this parameter only on file systems that have a very large average file size. On these file
systems it results in fewer extents per file and less fragmentation.
initial_extent_size is measured in file system blocks.
inode_aging_count
Specifies the maximum number of inodes to place on an inode aging list. Inode aging is used in
conjunction with file system Storage Checkpoints to allow quick restoration of large, recently
deleted files. The aging list is maintained in first-in-first-out (fifo) order up to maximum number
of inodes specified by inode_aging_count. As newer inodes are placed on the list, older inodes
are removed to complete their aging process. For best performance, it is advisable to age only a
limited number of larger files before completion of the removal process.
The default maximum number of inodes to age is 2048.
max_buf_data_size
The maximum buffer size allocated for file data; either 8K bytes or 64K bytes. Use the larger
value for workloads where large reads/writes are performed sequentially. Use the smaller value