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

HP-UX Handbook – Rev 13.00 Page 21 (of 47)
Chapter 14 Journaled File System (JFS)
October 29, 2013
on workloads where the I/O is random or is done in small chunks.
8K bytes is the default value.
inode_aging_size
Specifies the minimum size to qualify a deleted inode for inode aging. Inode aging is used in
conjunction with file system Storage Checkpoints to allow quick restoration of large, recently
deleted files. For best performance, it is advisable to age only a limited number of larger files
before completion of the removal process.
Setting the size too low can push larger file inodes out of the aging queue to make room for
newly removed smaller file inodes.
max_direct_iosz
The maximum size of a direct I/O request that are issued by the file system. If a larger I/O
request comes in, then it is broken up into max_direct_iosz chunks. This parameter defines how
much memory an I/O request can lock at once.
NOTE: This parameter should not be set to more than 20 percent of memory.
max_diskq
Limits the maximum disk queue generated by a single file. When the file system is flushing data
for a file and the number of buffers being flushed exceeds max_diskq, processes are blocked
until the amount of data being flushed decreases. Although this does not limit the actual disk
queue, it prevents flushing processes from making the system unresponsive.
The default value is 1 MB.
max_seqio_extent_size
Increases or decreases the maximum size of an extent. When the file system is following its
default allocation policy for sequential writes to a file, it allocates an initial extent which is large
enough for the first write to the file. When additional extents are allocated, they are progressively
larger because the algorithm tries to double the size of the file with each new extent. As such,
each extent can hold several writes worth of data. This is done to reduce the total number of
extents in anticipation of continued sequential writes.