Machines replication

Machines protection consists of several steps:

  1. Installing agents and configuring replication
  2. Getting consistent machines snapshots
  3. Detecting changes on machines between two snapshots
  4. Sending deltas to a DC with regard to WAN optimization and deduplication
  5. Storing of incremental backups in a DC with regard to the snapshot storage policies

Retrieving machines snapshots and detecting changes

Depending on the initial virtualization platform, it is possible to obtain consistent snapshots of machines in one of the following ways:

  • in case of replicating machines on VMware, getting snapshots of Windows and Linux machines is done with standard tools of VMware (VMware CBT API), leveraging a chain of internal API calls and snapshots as well as the means of the machine’s OS itself.
  • for Windows machines, consistent snapshots are acquired by means of Volume Shadow Storage (VSS) calls and tracking changes between two Application-consistent snapshots
  • for Linux machines, consistent snapshots are acquired by implementation of the VSS snapshot analog for block devices and sending changes to the snapshot store.


In case of a VMware infrastructure replication, VMware Tools must be installed on your virtual machines.

Sending deltas to storage. Data deduplication

Deltas are the accumulated changes since the last replication.

Sending changes to the DC is done using the customer agent secure HTTPS protocol. This constitutes the deduplication process - the customer application only sends data that is not yet stored for the given customer allowing to significantly save the amount of transferred items, reduce load on the network and, at times, accelerate replication of machines.

In addition to WAN deduplication, optimization also includes compression of the network traffic.

Creating a group of machines

Once a customer dashboard has been created as part of product’s initial configuration for replicating machines, navigate to the main page and select machine groups. Grouping machines allows to merge them by functionality or common parameters of replication schedule.

To create a group, click Add at the bottom of the Customer page.


It is possible to add any number of groups. By default, each group inherits global settings for a replication schedule and snapshot retention policies of a customer. Editing group settings will be described below. Note that group name must be unique within the customer.


Each customer must have at least one group. The Default group, which includes all machines that have not been added to other groups, is created automatically.

To move machines between groups, select them and click Move to group in the Actions menu. Note that if replication schedule and snapshot storage policies have not been redefined exclusively, the new group’s parameters will apply after transfer.

Machines replication and distribution between groups

Once groups have been created, you can proceed to replicate machines. To do this, follow the machine replication process (Section: ACP - Machine Replication Process) directly from the menu or through the group settings using the Replicate new platform menu item. The second option will automatically select a group for the machine during the relevant migration process step.


Select the type of a replicated platform.


Select a group where all the replicated machines will appear (machines can be redistributed between groups later). The last step is to download an agent, which is immediately ready to be installed on customer’s infrastructure.

Agent installation and configuration

VMware Agent requirements

Hystax VMware Replication Agent requires the following user permissions in vSphere (Role “VMware Consolidated Backup user” in vCenter):

  • Virtual machine - Configuration – Disc Lease
  • Virtual machine - Provisioning – Allow read-only disk access
  • Virtual machine - Provisioning – Allow virtual machine files upload
  • Virtual machine - Snapshot management – Create snapshot
  • Virtual machine - Snapshot management – Remove Snapshot

Permission to access CBT is necessary for a correct application work as well. To enable CBT:

Virtual machine → Configuration → Disc change tracking

Ports for correct agent work:

  • DR host - tcp/80, tcp/443
  • vSphere host - tcp/443
  • ESXi host(s) - tcp/udp/902
  • Send logs to the Acura cluster - udp/12201

Hystax VMware Replication Agent uses VMware snapshots and VMware CBT API in order to create a consistent replica of machines’ data.

This implies the following considerations regarding the VMware storage:

  • VMware snapshots consume storage to retain copy-on-write buffer, so it is recommended to have at least 10% free space available on VMware storage.
  • VMware puts additional load on storage while creating snapshots or running machines with existing snapshots.

Please consider that storage performance warning thresholds need to be adjusted in order to meet this increased load during replication.


The source machine must have VMware Tools installed manually prior to any replication procedures for it to display its network information in the target VMware ESXi correctly.

VMware Agent configuration

To edit the “hosts” file of a VMware replication agent:

  1. Go to the agent command line by pressing the “To console” button in the TUI.
  2. Edit /var/run/hosts file.
  3. Restart services for the changes to take effect by pressing the “Restart services” button in the TUI.

To change the hostname of a VMware replication agent, which is “hwragent” by default:

  1. Go to the agent command line by pressing the “To console” button in the TUI.
  2. Edit the /var/run/hostname file and change the hostname of the agent machine.
  3. Reboot the VMware VM gracefully for the changes to take effect.

Windows and Linux Agents requirements

Requirements for the correct work of a Windows agent:

  • Hardware:
    • Memory: 2 GB RAM
    • CPU: x64 processor
    • Disk space: 100 MB required for product installation and not less than 15% free space of the disk size for a VSS snapshots creation
  • Software:
    • Microsoft .NET Framework 4.0


Windows replication agent must be installed by the System Administrator or using Administrator privileges. Otherwise, it will not have enough permissions to use API or create snapshots and the replication will fail.

Requirements for the correct work of a Linux agent:
  • Hardware:
    • Memory: 500 MB RAM
    • Disk space: 100 MB required for product installation and not less than 15% free space of the disk size for snapshots creation
Ports needed for the correct work of agents:
  • Send data to Acura host - tcp/443
  • Send logs to Acura - udp/12201

Install Windows and Linux agents

To install a Windows or a Linux agent, just download the msi file or the deb / rpm package respectively and deploy it on a guest OS. After a successful installation, the agent will automatically register the machine in the system, so that it will appear in the machine list of the group selected in the previous step.

Install VMware agents

To install a VMware agent, download an .ova file and deploy one instance of the agent on each of the ESXi hosts of VMware vSphere. Note: VMware vSphere can issue a warning about the presence of an unknown configuration parameter for the virtual machine. The service parameter “hvragent” is added deliberately and it is not a security risk.

To deploy a new agent, follow the instructions below:

  1. Use VMware Web Client / vSphere Client / VMware fusion.
  2. Select a downloaded .ova template with the agent for deployment.


  1. Select a storage that the agent will be uploaded to.


  1. Select disk provisioning and network that have Internet access.


  1. Start the agent when deployment process is complete.

After starting machines that run agents, machines on the same ESXi host that have been recognized by agents will automatically appear in the list of customer machines in the selected group. The machines will be assigned with the “Not replicated” state (this allows excluding machines that are not intended for replication). To start replication, select the necessary machines and click Start replication in the Actions menu.

Agent logs can be found by clicking the To console button in the agent’s UI. The logs are stored in “/logs/hvragent.log”

To get the current network settings, use the file “/var/run/network/current-settings*.

To change the network settings (for example, if the agent can not get an IP address by DHCP), edit the file “/var/run/network/interfaces”. Once the settings have been changed, please reboot the agent.

Setting replication schedule

Once machines have appeared in the list and replication has been enabled for the specified machines, it is necessary to set replication schedules and snapshot storage policies (Sections: ACP - Replication schedule and ACP - Snapshot policy settings).



Settings can be changed globally for a customer, for each individual group or for individual machines.

Settings are inherited in the following way:

  • By default, global settings are applied to all groups and machines
  • Upon editing group settings, the new settings are applied to all machines (in the group or the ones added later) with the default settings, otherwise the settings of individual machines will still be valid.
  • Upon editing settings of a machine, only the one specific machine is affected, otherwise group settings or global settings apply.

Once these steps are completed, the machines will be replicated based on schedule and rules that have been set during the configuration.