The advanced VMkernel.Boot.isPerFileSchedModelActive parameter controls the per file I/O scheduling mechanism on VMFS and NFS 3 datastores. On the ESXi host, the mechanism is enabled by default. You can disable the mechanism using the Advanced System Settings dialog box.

If you turn off the per file I/O scheduling model, your host reverts to a legacy scheduling mechanism. The legacy scheduling maintains only one I/O queue for each virtual machine and storage device pair. All I/Os between the virtual machine and its virtual disks are moved into this queue. As a result, I/Os from different virtual disks might interfere with each other in sharing the bandwidth and affect each other's performance.

Note: Do not disable per file scheduling if you have the HPP plug-in and the latency sensitive threshold parameter configured for high-speed local devices. Disabling per file scheduling might cause unpredictable behavior.


  1. In the vSphere Client, navigate to the ESXi host.
  2. Click the Configure tab.
  3. Under System, click Advanced System Settings.
  4. Edit the value of the VMkernel.Boot.isPerFileSchedModelActive parameter.
    Option Description
    False Disable the per file scheduling mechanism.
    True (default) Reenable the per file scheduling mechanism.
  5. Reboot the host for the changes to take effect.