Limiting disk I/O from a specific virtual machine

Products

• VMware vSphere ESXi

Issue/Introduction

This article provides a method to limit the disk I/O for a specific virtual machine using the vSphere Client.

 

 

Environment

VMware vSphere ESXi 6.x

Resolution

To manually configure disk I/O limits for a virtual machine:

1. Power off the virtual machine in preparation for changing the configuration parameters.
2. Locate the virtual machine in the vSphere Client inventory.
3. Right-click the virtual machine and click Edit Settings.
4. Click the Resources tab.
5. Select Disk, and enter the desired IOPs value under Limit - IOPs for each disk. By default, this is set to Unlimited.
6. Start the virtual machine. The virtual machine I/O is limited to the specified values.

Note: These steps work for an ESXi 6.x  and above environment if the VMwaretools hardware version is less than 9. If your hardware version is not less than 9 use the VMware Web Client to access the same functionality. For more information, see Use Disk Shares to Prioritize Virtual Machines in the vSphere Web Client from the 

Use Disk Shares to Prioritize Virtual Machines

Additional Information

 

Examples

1. The following Examples explain the behavior for VMs  "ESXi 6.0 for NFS datastore".
   
   All limit values are consolidated per virtual machine per LUN.
   
   Examples for a virtual machine with four virtual disks:
   
   
• Example 1: All virtual disks located on one LUN. Each virtual disk IOPs set to 100 IOPs.
  
  As each disk is limited to 100 IOPs, the total IOPs for the datastore is 400 IOPs. If disks 1, 2, and 3 issue 10 IOPs each, disk 4 could issue 370 IOPs without being restricted.
  
  
• Example 2: Disks 1 and 2 on LUN A, disks 3 and 4 on LUN B. All limits are set to 100 IOPs per disk.
  
  The IOPs are consolidated to 200 IOPs to LUN A and 200 IOPs on LUN B. If disks 1 and 3 issue 10 IOPs each, disks 2 and 4 could issue 190 IOPs without being restricted.
  
  
• Example 3: All virtual disks located on one LUN. One disk is set to Unlimited, all other disks are set to 100 IOPs.
  
  As one of the disks on the LUN is set to Unlimited, the IOPs for the LUN are also Unlimited for that datastore.
  
  
  
2. The following Examples explain the behavior for VMs on "ESXi 6.0 and above for VMFS datastore" and "ESXi 6.5 for NFS datastore".
   
   The I/O Limiting behavior has been enhanced which will restrict the IOPs on each virtual disk based on Limit-IOPs value.
   
   Examples for a virtual machine with four virtual disks:
   
   
• Example 1: All virtual disks located on one LUN. Each virtual disk IOPs set to 100 IOPs.
  
  If disks 1, 2, and 3 issue 10 IOPs each, disk 4 could issue 100 IOPs as this is the limit.
  
  
• Example 2: Disks 1 and 2 on LUN A, disks 3 and 4 on LUN B. All limits are set to 100 IOPs per disk.
  
  If disks 1 and 3 issue 10 IOPs each, disks 2 and 4 could issue maximum of 100 IOPs.
  
  
• Example 3: All virtual disks located on one LUN. One disk is set to Unlimited, all other disks are set to 100 IOPs.
  
  IOPs is unlimited for the disk whose Limit is set to "Unlimited". All other disks could issue maximum of 100 IOPs.

 

Note: Steps to fallback to mechanism in "a" from "b" in "ESXi 6.0 and above for VMFS datastore" and "ESXi 6.5 for NFS datastore" is as follows:

Edit Per File I/O Scheduling

 

Alternate options for controlling disk usage

• Storage I/O Control (SIOC): This requires that datastores are not shared with non-vSphere workloads. For more information, see the Managing Storage I/O Resources section in the: 

  vSphere Resource Management

• Disk Shares: This does not provide absolute limits. For more information, see:
  
  
  • Use Disk Shares to Prioritize Virtual Machines in the  Use Disk Shares to Prioritize Virtual Machines