6.5.1

Table Of Contents
Scheduling Queues for Virtual Machine I/Os
By default, vSphere provides a mechanism that creates scheduling queues for every virtual machine file.
Each file, for example .vmdk, gets its own bandwidth controls.
This mechanism ensures that I/O for a particular virtual machine file goes into its own separate queue
and avoids interfering with I/Os from other files.
This capability is enabled by default. To turn it off, adjust the
VMkernel.Boot.isPerFileSchedModelActive parameter in the advanced system settings.
Edit Per File I/O Scheduling
The advanced VMkernel.Boot.isPerFileSchedModelActive parameter controls the per file I/O
scheduling mechanism. The mechanism is enabled by default.
Procedure
1 Browse to the host in the vSphere Web Client navigator.
2 Click the Configure tab.
3 Under System, click Advanced System Settings.
4 Under Advanced System Settings, select the VMkernel.Boot.isPerFileSchedModelActive
parameter and click the Edit icon.
5 Perform one of the following actions:
n
To disable the per file scheduling mechanism, change the value to No.
Note After you turn off the per file I/O scheduling model, your host reverts to a legacy
scheduling mechanism that uses a single I/O queue. The host maintains the single I/O queue for
each virtual machine and storage device pair. All I/O between the virtual machine and its virtual
disks stored on the storage device are moved into this queue. As a result, I/O from different
virtual disks might interfere with each other in sharing the bandwidth and affect each other's
performance.
n
To reenable the per file scheduling mechanism, change the value to Yes.
6 Reboot the host for the changes to take effect.
Use esxcli Commands to Enable or Disable Per File I/O
Scheduling
You can use the esxcli commands to change the I/O scheduling capability. The capability is enabled by
default.
vSphere Storage
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