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Backing up your data is especially important in any technological environment.  In virtual infrastructures, administrators must also be familiar with back up technology.  One back up method I was particularly interested in was snapshots.  Snapshots are useful in vSphere for safeguarding data in a virtual environment.  These snapshots can save and protect virtual machine settings, disk state, memory, and power settings.  Snapshots can also protect you from misbehaving applications or other practices that could lead to data failure.  A snapshot is a unique form of data preservation and useful for short term protection.

            Snapshots are useful in lots of different situations.  You can place a virtual machine in snapshot mode before an operating system upgrade.  This way, if the upgrade fails, the virtual machine could still easily revert to its former state.  Snapshots do not affect virtual hard disks or NFS file systems.    It is paramount to remember that snapshots are not long-term solutions.  They should not be used as a replacement for backups.

            When a user creates a snapshot, a delta disk is created for the virtual machine.  If memory is saved in the snapshot, the file will also save the memory and power state.  This delta disk will be used for all the disk writes.  It is important to understand that these delta disks only hold the differences between the current state and original virtual disk.  Snapshots are not full copies of a virtual machine.    That is why they are not a substitute for backups.  There is also a performance penalty for using snapshots which depends on the workload and duration of snapshots.

            While using snapshots operations, VMware tools allows drivers running their operating systems to pause.  This guarantees consistency for the virtual machines using snapshots.  However, levels of consistency may vary based on workloads.  Some of the restrictions for snapshots include PCI vSphere Direct Path.  This device is not supported.

            VM snapshots are like checkpoints for a VM.  They capture the virtual machine at a specific point in time.  They are an efficient storage method, however if used incorrectly they can begin to take up too much space.  It is better to remove them when they are no longer needed.