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An administrator wants to adjust disk resource allocation to ensure proper storage performance.
Which two mechanisms are available? (Choose two.)
A. Shares
B. Guarantee IOPs
C. Limit IOPs
D. Reservation
Correct Answer: AC
Explanation/Reference:
Use Disk Shares to Prioritize Virtual Machines
You can change the disk resources for a virtual machine. If multiple virtual machines access the same VMFS datastore and the same logical unit number (LUN), use disk shares to prioritize the disk accesses from the virtual machines. Disk shares distinguish high-priority from low-priority virtual machines.
You can allocate the host disk’s I/O bandwidth to the virtual hard disks of a virtual machine. Disk I/O is a host-centric resource so you cannot pool it across a cluster.
Shares is a value that represents the relative metric for controlling disk bandwidth to all virtual machines. The values are compared to the sum of all shares of all virtual machines on the server and, on an ESX host, the service console.
Disk shares are relevant only within a given ESX/ESXi host. The shares assigned to virtual machines on one host have no effect on virtual machines on other hosts.
You can select an IOP limit, which sets an upper bound for storage resources that are allocated to a virtual machine. IOPs are the number of I/O operations per second.
http://pubs.vmware.com/vsphere-4-esx-vcenter/index.jsp?topic=/com.vmware.vsphere.vmadmin.doc_41/vsp_vm_guide/configuring_virtual_machines/t_use_disk_shares_for_vms.html
