Guidelines for using the filemon command

There are several guidelines for using the filemon command.

• The /etc/inittab file is always very active. Daemons specified in /etc/inittab are checked regularly to determine whether they are required to be respawned.
• The /etc/passwd file is also always very active. Because files and directories access permissions are checked.
• A long seek time increases I/O response time and decreases performance.
• If the majority of the reads and writes require seeks, you might have fragmented files and overly active file systems on the same physical disk. However, for online transaction processing (OLTP) or database systems this behavior might be normal.
• If the number of reads and writes approaches the number of sequences, physical disk access is more random than sequential. Sequences are strings of pages that are read (paged in) or written (paged out) consecutively. The seq. lengths is the length, in pages, of the sequences. A random file access can also involve many seeks. In this case, you cannot distinguish from the filemon output if the file access is random or if the file is fragmented. Use the fileplace command to investigate further.
• Remote files are listed in the volume:inode column with the remote system name.

Because the filemon command can potentially consume some CPU power, use this tool with discretion, and analyze the system performance while taking into consideration the overhead involved in running the tool. Tests have shown that in a CPU-saturated environment:

• With little I/O, the filemon command slowed a large compilation by about one percent.
• With a high disk-output rate, the filemon command slowed the writing program by about five percent.