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Snapshots (replays) and virtual machine backups
56 Dell EMC SC Series: Best Practices with VMware vSphere | 2060-M-BP-V
14 Snapshots (replays) and virtual machine backups
Backup and recovery are important to any virtualized infrastructure. This section discusses several common
techniques to improve the robustness of virtualized environments such as using snapshots (replays) and
virtual machine backups.
14.1 Backing up virtual machines
The key to any good backup strategy is to test the backup and verify the results. There are many ways to
back up virtual machines, but depending on business needs, each solution is unique to each environment.
Testing and verification may prove that one solution works better than another does, so it is best to test a few
different options.
Since the subject of virtual machine backup is vast, this section only covers a few basics. For more
information about virtual machine backup strategies, consult VMware documentation.
14.1.1 Backing up virtual machines to tape or disk
Perhaps the most common methods of backing up virtual machines to tape are using third-party backup
software or using the backup client software installed within the guest. Options include:
Backup software using vStorage APIs for Data Protection (VADP): VADP is a successor to VMware
Consolidated Backup and provides an integrated method to back up virtual machines for backup solutions
such as Dell NetVault™ Backup for VMware. For more information, see VMware vSphere Storage APIs -
Data Protection (VADP) FAQ in the VMware Knowledge Base.
Backup client loaded within the guest: Using this method, traditional backup software is loaded within the
guest operating system, and the data is backed up over the network to a backup host containing the tape
drive. Depending on the software used, it only performs file-level backups, but sometimes, it can include
additional capabilities for application-level backups.
14.1.2 Backing up virtual machines using snapshots
The options for backing up virtual machines using SC Series snapshots are described as follows:
Snapshots scheduled from within the DSM client: From within the DSM client, a snapshot schedule
(replay profile) can be created to schedule snapshots of virtual machine volumes. Usually, using snapshots to
back up virtual machines is enough to perform a standard recovery. Remember, snapshots can only capture
data that has been written to disk, and therefore the virtual machine data is preserved in what is called a
crash-consistent state. In other words, when recovering the virtual machine, the data is recovered as if the
virtual machine had lost power. Most modern journaling file systems such as NTFS or EXT3 are designed to
recover from such states.
Snapshots taken using Dell Replay Manager software: Since virtual machines running transactional
databases are more sensitive to crash-consistent data, Replay Manger utilizes the Microsoft VSS framework
for taking snapshots of VSS-aware applications. This software package will ensure that the application data is
in a consistent state before performing the snapshot.
Snapshots taken using Dell scripting tools: For applications that need a custom method for taking
consistent snapshots of the data, Dell has developed two scripting tools: