Product : Citrix, XenServer/7.3, Enterprise
Feature : Storage QoS, Storage, Network and Storage
Content Owner:  Roman Macek
Summary
Basic
Details
Virtual disks on block-based SRs (e.g. FC, iSCSI) have an optional I/O priority Quality of Service (QoS) setting. This setting can be applied to existing virtual disks using the xe CLI.
Note: Bare in mind that QoS setting are applied to virtual disks accessing the LUN from the same host. QoS is not applied across hosts in the pool!