Suspending and Resuming Virtual Machines

VMware ESX Server 1.5
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Suspending a virtual machine, then later resuming its operation, can speed provisioning tasks - for example, deployment of standby servers. VMware ESX Server supports two configurations for resuming a suspended virtual machine.

You can suspend a running virtual machine at any time, then resume operation, suspend at a later time, then resume with the machine in the second state, and so on.
You can suspend a virtual machine at any desired point in its operation, then lock in the suspended state at that chosen point. Any time you restart the virtual machine, it resumes in the same state - the state it was in when you first suspended it.

Note: You should not change a configuration file after you suspend a virtual machine, since the virtual machine does not resume properly if the configuration file is inconsistent with the suspended virtual machine. Also, you should not move any physical disks or change the name of any VMFS file systems that the virtual machine uses. If you do, the virtual machine will not be able to access its virtual disks when it resumes.

You can also set the configuration of each virtual machine so the file that stores information on the suspended state is saved in a location of your choice.

Note: You cannot suspend a virtual machine configured to use more than 2GB of RAM.

Setting the Suspend Directory

When a virtual machine is suspended, its state is written to a file with a .vmss extension. By default, the .vmss file is written to the same directory as the configuration file. Similarly, when a virtual machine is being resumed, ESX Server looks for the .vmss file in the same directory as the configuration file.

You may want to select a different location for better performance or to avoid running out of space on the partition that holds the virtual machine directories.

When you change the directory where the suspended state file for a virtual machine is stored, the virtual machine must be powered off. Then follow these steps:

Log in to the VMware Management Interface, point to the terminal icon for the virtual machine you want to change, then click Edit Configuration. Scroll to the bottom of the page to the Misc. section and select the desired suspend location.
For fastest suspend and restore operations, select VMFS Volume and choose the appropriate VMFS volume from the drop-down list. ESX Server automatically adds a suffix to the name of the suspended state file to ensure that one virtual machine does not overwrite the suspended state file of another.
If you want to save the suspend file in a different directory, specify the path in the Other location entry field.
Click Save Changes.

Enabling Repeatable Resumes

When you suspend a virtual machine in the usual way, by clicking the suspend button on the remote console or in the management interface, ESX Server writes a file with a .vmss extension. This file contains the entire state of the virtual machine. When the virtual machine is resumed, its state is restored from the .vmss file. The .vmss file is then modified while the virtual machine is running. This means that, in normal operation, the .vmss file cannot be used to resume a virtual machine again from the original suspended state.

If you do want to be able to resume a virtual machine in the same state repeatedly - for example, to have a hot-standby virtual machine in a particular state so it is ready to take over for a failed server - take the following steps:

Shut down and power off the virtual machine.
Be sure all virtual disks used by the virtual machine are set to nonpersistent mode.
On the main page of the VMware Management Interface, move the mouse pointer above the terminal icon for the virtual machine you want to set for repeatable resume mode. A context menu appears. Choose Edit Configuration to go to the Configure VM page, where you can set the disk mode. You have access to this page only when the virtual machine is powered off.
After making your changes, click Save Changes. ESX Server saves your changes and takes you to the details page for the virtual machine.
Next to Repeatable Resume, click On to enable the repeatable resume feature.
Power on the virtual machine.
Using the remote console, take the steps necessary to reach the state in which you want to suspend the virtual machine.
Click Suspend to activate repeatable resume.
After you do this, each time you resume the virtual machine, it will resume from the suspend point you have set. When you click Power Off, the virtual machine will power off, ready to resume at the suspend point you have set.

To turn off the repeatable resume feature, take the following steps while the virtual machine is running.

On the main page of the VMWare Management Interface, click the name of the virtual machine you want to take out of repeatable resume mode.
On the details page for the virtual machine, next to Repeatable Resume, click Off to disable and deactivate the repeatable resume feature.

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