6.7

When you take a snapshot, other activity that is occurring in the virtual machine might affect the snapshot
process when you revert to that snapshot. The best time to take a snapshot from a storage perspective, is
when you are not incurring a large I/O load. The best time to take a snapshot from a service perspective
is when no applications in the virtual machine are communicating with other computers. The potential for
problems is greatest if the virtual machine is communicating with another computer, especially in a
production environment. For example, if you take a snapshot while the virtual machine is downloading a
file from a server on the network, the virtual machine continues downloading the file and communicating
its progress to the server. If you revert to the snapshot, communications between the virtual machine and
the server are confused and the file transfer fails. Depending on the task that you are performing, you can
create a memory snapshot or you can quiesce the file system in the virtual machine.
Memory Snapshots The default selection for taking snapshots. When you capture the virtual
machine's memory state, the snapshot retains the live state of the virtual
machine. Memory snapshots create a snapshot at a precise time, for
example, to upgrade software that is still working. If you take a memory
snapshot and the upgrade does not complete as expected, or the software
does not meet your expectations, you can revert the virtual machine to its
previous state.
When you capture the memory state, the virtual machine's files do not
require quiescing. If you do not capture the memory state, the snapshot
does not save the live state of the virtual machine and the disks are crash
consistent unless you quiesce them.
Quiesced Snapshots When you quiesce a virtual machine, VMware Tools quiesces the file
system of the virtual machine. A quiesce operation ensures that a snapshot
disk represents a consistent state of the guest file systems. Quiesced
snapshots are appropriate for automated or periodic backups. For example,
if you are unaware of the virtual machine's activity, but want several recent
backups to revert to, you can quiesce the files.
If the virtual machine is powered off or VMware Tools is not available, the
Quiesce parameter is not available. You cannot quiesce virtual machines
that have large capacity disks.
Important Do not use snapshots as your only backup solution or as a long-term backup solution.
Change Disk Mode to Exclude Virtual Disks from Snapshots
You can set a virtual disk to independent mode to exclude the disk from any snapshots taken of its virtual
machine.
Prerequisites
Power off the virtual machine and delete any existing snapshots before you change the disk mode.
Deleting a snapshot involves committing the existing data on the snapshot disk to the parent disk.
vSphere Virtual Machine Administration
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