Allocate storage I/O resources to virtual machines based on importance by assigning a relative amount of shares to the virtual machine.

Unless virtual machine workloads are very similar, shares do not necessarily dictate allocation in terms of I/O operations or megabytes per second. Higher shares allow a virtual machine to keep more concurrent I/O operations pending at the storage device or datastore compared to a virtual machine with lower shares. Two virtual machines might experience different throughput based on their workloads.


Launch the vSphere Client and log in to a vCenter Server system.


  1. Select a virtual machine in the vSphere Client inventory.
  2. Click the Summary tab and click Edit Settings.
  3. Click the Resources tab and select Disk.
  4. Select a virtual hard disk from the list.
  5. Click the Shares column to select the relative amount of shares to allocate to the virtual machine (Low, Normal, or High).
    You can select Custom to enter a user-defined shares value.
  6. Click the Limit - IOPS column and enter the upper limit of storage resources to allocate to the virtual machine.
    IOPS are the number of I/O operations per second. By default, IOPS are unlimited. You select Low (500), Normal (1000), or High (2000), or you can select Custom to enter a user-defined number of shares.
  7. Click OK.


Shares and limits are reflected on the Resource Allocation tab for the host and cluster.