Symantec logo



vxiod - start, stop, and report on Veritas Volume Manager I/O threads



vxiod [-f ] [set count]


The vxiod utility starts, stops, or reports on Veritas Volume Manager (VxVM) I/O kernel threads. An I/O thread provides a process context for performing I/O in VxVM.

When the vxio module is loaded, 16 I/O threads are created, plus 2 threads per additional CPU for a system with more than 8 CPUs, up to a maximum of 64 threads. At least one I/O thread must be running while the vxio module is loaded, and the number of I/O threads cannot be forced to zero.

When invoked with no arguments, vxiod prints the current number of I/O threads to the standard output.

The number of threads that is required for handling I/O requests depends on the system load and usage. If volume recovery seems to proceed more slowly at times, it may be possible to improve its performance by increasing the number of I/O threads up to a maximum of 64.



When invoked with the set keyword, vxiod creates the number of I/O threads specified by count. If more volume I/O threads exist than are specified by count, the excess processes terminate. If more than the maximum number (64) are specified, the requested number is silently truncated to that maximum.



This option has no effect from release 5.0 onward. The number of I/O threads cannot be reduced to zero.


The vxiod utility prints a diagnostic on the standard error, and exits if an error is encountered. If an I/O request occurs within a I/O thread, the state of that I/O request is not reflected in the exit status for vxiod. Otherwise, vxiod returns a non-zero exit status on error.

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



The device used to report on and start volume I/O threads.


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

Depending on the operating system, VxVM I/O threads may not appear in the list of processes that is output by the ps command. The number of I/O threads that is currently running can be determined by running vxiod.


fork(2), ps(1), vxconfigd(1M), vxdctl(1M), vxintro(1M)