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.
- In the vSphere Client, navigate to the ESXi host.
- Click the Configure tab.
- Under System, click Advanced System Settings.
- 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.
- Reboot the host for the changes to take effect.