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Back up virtual machines and clusters

Flexible Security

Article from ADMIN 64/2021
Vembu BDR Suite provides comprehensive software that supports flexible configuration when backing up virtual production operations.

Vembu BDR Suite [1] helps you back up Hyper-V and VMware ESXi environments with up to 10 virtual machines (VMs) free of charge. In this article, I back up a Hyper-V host and start by installing an agent for the connection – the Vembu integration service (VIS) – that is also capable of backing up server-based services such as Exchange or SQL Server on the VMs.

You do not need to install any additional software on the virtual machines themselves. In addition to standalone Hyper-V hosts, you can also back up clusters with Vembu. For the backup, the vendor draws on the Hyper-V volume shadow copy service (VSS). The VMs are therefore included in the backup, instead of just copying the virtual hard drives and their data.

Vembu BDR Suite also relies on resilient change tracking (RCT) in Windows Server 2016 and 2019, a feature that allows backup software to detect which data has changed on the virtual disks since the last full backup so that only the changed data is saved. In this case, the virtual hard drive consists of blocks. If you perform a full backup, all blocks are backed up to a repository.

However, for the next backup, you will only want to back up the changed blocks. The change block tracker creates a bitmap of all the blocks on the virtual hard drive. As soon as the data in a block changes, it is marked accordingly. At the time of a backup, the backup software only needs to check the bitmap for all blocks that have changed since the last backup and then simply backs up the changed blocks.

This method has been possible without additional functions since Windows Server 2016 with RCT. RCT creates three bitmaps: one in memory and two on the hard disk, which ensures that the bitmaps are not lost. As long as the VM is running, the backup software checks the bitmap and only backs up the changed blocks when an incremental backup is requested. If a VM is migrated or a power failure occurs, the backup software still has two bitmap files from which to choose.

The RCT file is used during normal operation. In case of a sudden power failure or a similarly serious event, the modified region table (MRT) file can also help. This table is maintained in write-through mode and has coarser tracking granularity. In the event of a sudden power failure, the MRT file still provides a record of what has changed on the disk and guides the back up of data on recovery. The technology thus accelerates and simplifies incremental backups.

Functions and Limitations

Backups are easy to perform with the features included in the free edition of Vembu BDR Suite. As mentioned, the free version supports VMware ESXi and Hyper-V; you can also connect to vCenter with the free version. Up to 10 VMs are supported, and 10 EC2 instances can be backed up in Amazon Web Services (AWS). The same applies to services in Microsoft 365 and Google G Suite. The limit is 10 user accounts and their data. Backups of conventional Windows servers are also possible, as well as up to 10 workstations. You can also include Mac computers in addition to your Windows computers.

You can back up the VMs on Hyper-V hosts to local disks; CSV files, SMB shares, and Storage Spaces Direct are also supported. The free version is already capable of backing up applications in the VMs, including Exchange Server and SQL Server, among others, and can perform the backups online and delete transaction logs.

If you are satisfied with the product overall but need to back up more than 10 VMs, you can opt for one of the commercial editions. The costs are from $108 per CPU socket for the Standard Essentials edition to $360 for the Enterprise edition. The VMs to be backed up also need to be licensed. The prices are $18 for the Standard Essentials edition and $60 for the Enterprise edition.

Installing Vembu BDR Suite

The suite does not need to be installed on the Hyper-V host itself; instead, the connection and backup take place over the network. After the install, the functions of the Enterprise Edition can initially be used for 30 days, after which the software switches to Free mode. Free mode can also be enabled at any time beforehand; the settings for the editions can be found under Management | BDR Edition , which is where you can activate the functions of the Free Edition immediately after the install, as well the functions of the other editions, provided you have licensed the product.

The Vembu BDR Suite management data end up in a PostgreSQL database that's installed on a backup server when the suite is installed and does not contain the data of the virtual hard drives themselves, only the information of the backup for recovery and management. During the install, you specify the web console port and the back support. The installation wizard displays the default data in the window. You can also specify the username for accessing the administration interface and the corresponding password during the installation.

After you select from the various options, the wizard starts the installation. Afterward, you need to check in system services management whether the VembuBDR system service is running and whether the user account is correct. Parallel to the web interface, BDR also offers the Vembu agent interface on the server. From the context menu of the icon, you can restart the system service if necessary. The agent also displays messages telling you whether backups completed successfully or terminated with errors. These messages can also be disabled in the context menu.

To connect Hyper-V hosts, you need to start the VembuBDR system service with a domain account that is authorized to install an agent and perform tasks on the Hyper-V hosts. If the authorization is not sufficient, the wizard for connecting a new Hyper-V host will report an error to match.

Connecting the Hyper-V Host

Once the system service is started, you can open the web interface and log in with the user account you specified during installation. To back up Hyper-V hosts, first go to Backup | Configure Backups | Microsoft Hyper-V , which is where you add the servers that have the VMs you want to back up.

When adding Hyper-V hosts, use the Add Hyper-V Servers or Add-Hyper-V Clusters side tab to select the type of host you want to connect to (Figure 1). In the following, I assume you are setting up a standalone Hyper-V host because in most cases clusters have more than 10 VMs.

Figure 1: A Hyper-V backup in BDR starts with adding the virtual servers.

In the upper field, enter the name of the Hyper-V host. For Add Credentials , enter the credentials for accessing the Hyper-V host. For Hyper-V backup, an agent must be installed on the host (see the "Access Authorizations as a Source of Error" box). The various logins can be managed at any time under Infrastructure | Credentials . The item Management | BDR Clients | List Client Agents lets you view the currently connected servers, including the version of the client, in the course of connecting the host. You have to confirm the install agent prompt to connect the Hyper-V host.

Access Authorizations as a Source of Error

To back up VMs on a Hyper-V host, communication between the Vembu BDR server and the Hyper-V host must be working. To install the agent, copy the installation file to the admin$ share of the host. If the Hyper-V host connection does not work, you need to check whether you are allowed to access the share from the Vembu server. If this does not work, you can use a checklist from Vembu [2] to track down the problem.

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