vxiod(ADM)

vxiod - start, stop, and report on Volume Manager kernel daemons

Synopsis

vxiod
vxiod [ -f ] set count

Description

The vxiod utility starts, stops, or reports on Volume Manager I/O daemons. An I/O daemon is a process that provides a process context for processing any work that needs to be done to process Volume Manager I/O. Volume Manager I/O daemons are not required for proper operation, though not having any I/O daemons may result in a substantial reduction of system performance.

Operation

When invoked with no arguments, vxiod prints the current number of volume I/O daemons on the standard output.

When invoked with the set keyword, the number of daemons specified by count will be created. If more volume I/O daemons exist than are specified by count, then the excess processes will be terminated. If more than the maximum number are created (currently 64), the requested number will be silently truncated to that maximum.

The number of daemons to create for general I/O handling is dependent on system load and usage. It is generally not necessary to start more than one daemon for each CPU on the system. If volume recovery seems to proceed slower at some times, then it may be worthwhile to create more daemons.

Each I/O daemon starts in the background and creates an asynchronously-running process, which detaches itself from the controlling terminal and becomes a volume I/O daemon. The vxiod utility does not wait for these processes to complete.

Options

-f: Force the kill of the last I/O daemon. Without this option, the I/O daemons can only be reduced to one.

Exit codes

The vxiod utility prints a diagnostic on the standard error, and exits if an error is encountered. If an I/O occurs within a forked I/O daemon process, then the I/O is not reflected in the exit status for vxiod. Otherwise, vxiod returns a nonzero exit status on errors.

Usage errors result in an exit status of 1 and a usage message. If the requested number of daemons cannot be created, then the exit status is 2, and the number of daemons that were successfully started is reported. If any other error occurs, the exit status is 3.

Files

/dev/vxiod: The device used to report on and start volume I/O daemon processes.

Notices

Volume Manager I/O daemons cannot be killed directly through the use of signals.

The number of Volume Manager I/O daemons currently running can only be determined by running vxiod; I/O daemons do not appear in the list of processes produced by ps(C).

References

ps(C), vxconfigd(ADM), vxdctl(ADM), vxintro(ADM), fork(S), vxio(HW), vxiod(HW)