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A vSphere administrator enables Fault Tolerance on a powered off virtual machine that has the following configuration:
The virtual machine’s single thin provisioned virtual disk is sized at 100GB.
The datastore that houses the virtual machine has 120GB of free space.
After Fault Tolerance has been configured, another administrator attempts to use Enhanced vMotion to move a 30GB virtual machine file into the same datastore and receives an error.
What condition could cause this behavior?
A. Fault Tolerance inflated the virtual machine’s virtual disk file.
B. Fault Tolerance created a temporary logging file on the same datastore.
C. Fault Tolerance created a secondary copy of the virtual machine’s virtual disk file.
D. The Fault Tolerance logging file ran out of disk space.
Correct Answer: A
Explanation/Reference:
Explanation:
Fault Tolerance (FT) in VMware vSphere provides continuous availability for a virtual machine (VM) in the event of server failures by creating a live shadow instance of a virtual machine that is always up-to-date with the primary virtual machine. In the event of a hardware failure, FT automatically triggers failover to the secondary VM. After a failover, FT automatically creates a new, secondary virtual machine to provide continuous protection for the VM.
FT requires that multiwriter mode is possible on the VMDK to enable both the primary and secondary FT VMs to access the same disk. To use disks in multiwriter mode, the format must be Thick Provision Eager Zeroed.
In this question, the VM has a single thin provisioned virtual disk. When you enable FT on a VM, and that VM is using a thinly provisioned VMDK, that VMDK is inflated with zeroes as it is converted to a Thick Provision Eager Zeroed disk.
Incorrect Answers:
B: A temporary logging file would not be created on the VMDK. Therefore, this answer is incorrect.
C: FT does not create a copy of the VMDK. It uses multiwriter mode to use the existing VMDK. Therefore, this answer is incorrect.
D: It is unlikely that FT logging would use up the disk space. The VMDK being inflated with zeros until it uses the full 100GB assigned to the disk needs to happen before FT can be enabled and is likely to cause the issue described in this question. Therefore, this answer is incorrect.
References:
http://blogs.vmware.com/vsphere/2012/03/thin-provisioning-whats-the-scoop.html
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1033570