Overview

Snapshots

Virtual machine snapshots keep the state and data of a virtual machine at a specific point in time. You can create multiple snapshots to preserve multiple states for a virtual machine.

Snapshots can be very useful, though there are a few points that need to be considered:

• For each snapshot there will be a placeholder disk, containing the delta between the sets. If the base disks are deleted, the snapshot files are not sufficient to restore a virtual machine.
• The snapshot file continues to grow in size when it is retained for a longer period or during massive data transaction (e.g. data migrations) and can cause the storage location of the snapshot to run out of space and impact the system performance.

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Warning

• It is therefore not recommended to create snapshots of a VM before doing a data migration into this VM.

• It is not recommended to create snapshots of very large VMs or of VMs with a high data change rate, as it significantly can impact the performance of those VMs.

• When VMs have high I/O count, the consolidation of the snapshots can take a huge amount of time and stun the virtual machine.

• Backups can't be restored when having an active snapshot of a virtual machine.

Limitations

These facts lead to restriction for snapshot handling within the Enterprise Service Cloud according to VMware KB1025279

• Maximum 3 snapshots per virtual machine
• Maximum retention time of 72h hours

Preconditions and basic requirements

The Snapshot policy can be configured through an administrator. This service will allow following configurations:

• The maximum number of snapshots per business group
• Retention time of snapshot (in hours) per business group
• Periodicity of snapshot housekeeping job (in hours) per business group

In order to use the services you have to configure the following as a pre-requisites:

• Network administrator of the tenant which will be entitled to Configure Snapshots Service.

Image-based Backup

Backup & Restore is a set of services that allows a user to restore a Virtual Machine to a desired previous point in time. These services provide scheduled backup on deployed Virtual Machines. Once backed up, the user can restore the hard disk data in case of data loss or unintentional change. In case of deletion of a Virtual Machine it can be restored from the available backups.

Preconditions and basic requirements

Only authorized users can use Backup & Restore.

States

Virtual Machines with available backup have the following states:

• Running
• Suspended
• Stopped
• Deleted (Note: Only available for a Virtual Machine with available backup.)

Actions

• Restore Data
• Restore to New
• Restore File or Folder
• Create Backup
• View Backup Status

For more details see here.

Functions

When adding a Data Protection, a user can choose the desired backup policy for Imaged-Based Backups (IBB) (which defines, for example, the retention time of the IBB backups and their backup schedule). For more details see here.

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Note

Swisscom cannot guarantee that the backup of a VM will take place every day at the same time. Only one backup-window is defined, which will start i.e. at 8pm for all VM's. The duration depends on the number of VMs and the amount of new data which need be backed up.

Backup Option Quiesced

When the virtual machine is powered on during the creation of the snapshot, VMware Tools is used to quiesce the file system in the virtual machine. Quiescing a file system is a process of bringing the on-disk data of a physical or virtual computer into a state suitable for backups. This process might include such operations as flushing dirty buffers from the operating system's in-memory cache to disk or other higher-level application-specific tasks.

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Note

Quiescing indicates pausing or altering the state of running processes on a computer, particularly those that might modify information stored on disk during a backup, to guarantee a consistent and usable backup. Quiescing is not necessary for memory snapshots; it is used primarily for backups.

Custom Quiescing Scripts

You can use custom quiescing scripts inside Windows or Linux virtual machines which are often used by third-party backup modules that integrate with VMware APIs for Data Protection (VADP). Find more information here.

Requirements

Check if your Operating System support application-consistent (for older imported OS) and the VSS components in VMware Tools need to be installed.

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Important

Swisscom cannot guarantee a successful image based backup if quiescing is activated, as this option can cause a VMware snapshot to fail because of configurations within the guest OS (e.g. failing vss providers in windows guest OS). If a VMware snapshot cannot be created successfully, the image based backup will fail.