Frequently Asked Questions - Virtual Server Agent for VMware

Table of Contents

How can I calculate the number of licenses required for VMware?

Generate a Virtual Machine Infrastructure Report to get a summary of protected and unprotected virtual machines that you can use as a basis for requesting capacity licenses or socket licenses for VM protection.

How does the virtualization client perform automatic load balancing of backup jobs?

The virtualization client enables automatic load balancing of backup jobs across multiple proxy computers. The CommServe will attempt to contact a proxy from the list of proxies starting with the first. Once a proxy is successfully contacted it will act as the coordinator for the remainder of the job. The coordinator proxy will contact the remaining proxies in the list. Any proxies that are not available will not be utilized for the current job attempt.

Once all of the proxies to be used for the job are known, the coordinator will distribute the virtual machines among the available proxies. The decision of which proxy to use for a given virtual machine is based on which proxy is the best path for backing up that virtual machine. The following rules are used to determine the best path for backing up a virtual machine:

  1. Virtual machines will be backed up by proxies running as virtual machines on the same host.
  2. Virtual machines will be backed up by proxies running as virtual machines on hosts that have access to the datastore.
  3. Virtual machines will be backed up by proxies that are on the same subnet as the virtual machine’s host.
  4. The remaining virtual machines will be distributed evenly across the proxies.

Note: In a SAN environment, LUNs must be accessible to all proxies. Proxies on the same subnet are preferred, and the remaining virtual machines are distributed evenly across all available proxies.

For Example: a vCenter has three ESX servers, ESX1, ESX2 and ESX3

ESX1 hosts 2 virtual machines (VM1, VM2) and hosts Proxy1

ESX2 hosts 1 virtual machine (VM3), and hosts Proxy2

ESX3 hosts 1 virtual machine (VM4)

Then,

VM1 will be backed up by proxy1 because they are on the same host.

VM2 will be backed up by proxy1 because they are on the same host.

VM3 will be backed up by proxy2 because they are on the same host.

VM4 will be backed up by proxy2 because it only has one VM assigned.

The backup streams will also be distributed among the running proxies based on the number of virtual machines to be processed and while ensuring that all proxies that have virtual machines to process are being utilized.

To disable the virtual machine distribution logic, you can configure any of the following additional settings to provide equal distribution of virtual machines across the available proxies:

If one of the proxies becomes unavailable during the backup, the virtual machines allocated to that proxy will be distributed among the remaining proxies. Now if the proxy becomes available again when the same backup job is running, it will not be used for backup automatically. However, if you suspend the backup job and resume it again, the coordinator will allocate virtual machines to that proxy again.

Why is the backup throughput very low during the full backup?

If you are performing a full backup of virtual machines which have thin provisioned disks on NFS datastore, the backup throughput may become very low. VMware does not support the retrieving allocated blocks on NFS volume. Therefore, if a NFS datastore has a thin provisioned disk, the software reads the complete disk during the full backup. This reduces the backup throughput during the full backup.  In case of incremental backups, software uses Change Block Tracking (CBT) and thus reads and backs up only the changed data.

For more information, refer to “Changed Block tracking on Virtual disks" section in the following document:

http://pubs.vmware.com/vsphere-51/topic/com.vmware.ICbase/PDF/vddk51_programming.pdf

If the Thin provisioned disk is on VMFS volume, the software reads and backs up only the allocated part of the disk.

Can I back up fault tolerance virtual machines using the Virtual Server iDataAgent?

The VMware fault tolerance architecture does not allow VM Snapshot creation. Therefore, you cannot backup fault tolerance virtual machines. For more information about backing up fault tolerance virtual machines, refer to http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&externalId=1016619&sliceId=1&docTypeID=DT_KB_1_1&dialogID=381700304&stateId=1 0 381710452

Why is an incremental backup converted to a full backup after an in-place restore?

After performing an In-place restore, the first run backup job will always be converted to a Full backup. The system assumes that it is a newly created virtual machine and hence defaults to a full backup.

How do I manually install a new version of VDDK on a VSA proxy?

Version 6.0.2 of the VDDK is automatically installed when you install the Virtual Server Agent.

VDDK files should never be placed in the VDDK installation in the Commvault base directory.

To install a newer version of VDDK on a 64-bit computer, perform the following steps:

  1. Create a new VDDK install folder on the proxy computer (for example, C:\Program Files\VMware\VMware Virtual Disk Development Kit\).

    This folder structure already exists if a previous manual 64-bit installation has been performed.

  2. Download the VDDK package from the VMware download site and extract the files. Copy the bin and lib folders to the new VDDK install folder on the proxy computer.
  3. Create the following registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\VMware, Inc.\VMware Virtual Disk Development Kit

  4. Under that registry key, create the InstallPath string and set the value as the VDDK install folder you created for the VDDK executables (for example, C:\Program Files\VMware\VMware Virtual Disk Development Kit\).
  5. Go to the bin folder under the new VDDK install folder and run the file vstor2install.bat file to install the file-level driver.

For more information see Virtual Disk Development Kit 6.0.2 Release Notes.

How do backup and restore operations handle independent/RDM disks?

If a virtual machine undergoing a backup job includes independent disks or physical RDMs, those disks will be skipped.

If a subclient contains virtual machines with independent disks/physical RDMs, the backup job will always complete with the status "Completed w/ one or more errors". However, if you configure the IgnoreUnsupportedDisks additional setting on the proxy computer, the backup job will complete successfully.

If the Unconditionally overwrite VM with the same name option is used when restoring a virtual machine that has independent disks, the independent disks and their VMDKs are removed from the datastore and are not restored.

How do backup and restore operations handle virtual RDM disks?

Virtual RDMs are protected by the backup job (but not during SnapProtect backup). However at the time of restore, the data is restored as a regular VMDK on a datastore. A virtual RDM is not re-created and the data is not restored to the virtual RDM’s device.

Using the Virtual Server Agent in HotAdd mode configurations

  • When deploying the Virtual Server Agent, install the software on a datastore with the largest VMFS block size. This is necessary to ensure that the Virtual Server Agent can mount and back up virtual machines residing on all datastores.
  • Helper virtual machines are not required for HotAdd Virtual Server Agent servers using VADP.

What happens if a virtual machine is deleted in the vCenter and a new virtual machine with the same name is created?

In this scenario, even though the name of the virtual machine is same, the new virtual machine will have different GUID/UUID. Therefore, it is recommended to perform following steps:

  1. In the CommCell console, delete the virtual machine client from the list of client computers
  2. Perform the backup of the virtual machine. A client will get created again for the virtual machine.

If you do not perform these steps, a new client will get created for the virtual machine with name as follows: <original_virtual_machine_name>_1.

How is white space handled in virtual machine capacity licensing?

When capacity licensing is used, the used space as reported by the guest OS for the virtual machine is reported against licensed capacity. For example, if the guest OS shows 20GB used on a 100GB disk, 20GB is what counts against the licensed capacity. This is the case even if a different figure is reported for VM disks on the datastore, and is not affected by deduplication or compression.

What are the requirements to enable thin provisioned disk restores?

Disk level backups can use allocated block tracking, which is part of VMware Changed Block Tracking (CBT). Allocated block tracking identifies portions of the virtual machine disk that have not been used, so those portions can be skipped during backup or restore. In 10.0, disk restores can reclaim unused space even if allocated block tracking is not enabled.

During disk restore operations, writes of empty data are automatically discarded if the target disk is thin or eager zeroed. This enables thin provisioned disks to be restored to and from NFS datastores or for other VMDKs. Depending on the state of the data inside the virtual machine, it may also be possible for the restore to discard empty data that was previously allocated. The restore recovers all space that is reported in use (not zeroed out), so the restored VMDK can be larger than the size that was reported by the guest OS.

How can I limit VSA user access to specific resource pools or ESX hosts?

You can define users and provide them with role-based privileges in vCenter at any desired level: vCenter, datacenter, ESX host, resource pool, or virtual machine.

  1. On the vCenter server, define a local user who should have access to a specific level.
  2. In vCenter, define a role with the required permissions.
  3. At the desired level in vCenter, add permissions for the user and role.
  4. In the CommCell, add the user information to the Virtual Server instance properties.

For detailed steps, see Add a Custom User with Limited Scope.

Are Storage Spaces supported for backups and restores?

Storage Spaces is a  feature in Windows 8 and Windows Server 2012 that enables drives to be grouped into storage pools to appear as virtual drives in Windows File Explorer.

You can use the Virtual Server Agent to back up virtual machines and disks to Storage Spaces; but metadata collection is not supported for Storage Spaces. To retrieve guest files, restore the full virtual machine or virtual machine disk files.

How is capacity licensing calculated for virtual machines?

Virtual machine backup job data for capacity licensing usage is calculated as follows:

  • For streaming backups and backup copy jobs, the capacity usage is based on the guest size for all virtual machines being backed up.
  • For SnapProtect backups, the capacity usage is based on the application size for the virtual machines being backed up.

In the License Summary Report, the Job Size column lists guest sizes for virtual machines included in full or synthetic full streaming backups (including backup copy jobs) and application sizes for snapshots. 

Capacity usage is summarized as follows:

  • Virtual machine streaming backups are included in the Data Protection Enterprise Infrastructure or Data Enterprise Core Infrastructure license count (depending on the storage policy configuration).
  • Backup copy operations are included in the Data Protection Enterprise Infrastructure license count.
  • Archived VMs are included in the Data Archive Enterprise Infrastructure license count.
  • SnapProtect backups are included in the Data Protection Snapshot count.

When the same virtual machine is included in multiple backup jobs, only one of the jobs counts against capacity usage. If a virtual machine is included in multiple subclients, the latest backup provides the size included in overall capacity usage. If a virtual machine is included in both backups and archiving jobs, the guest size for the VM counts toward the Data Protection Enterprise Infrastructure or Data Enterprise Core Infrastructure license.

  • Service Pack 5 introduced capacity licensing based on guest VM size. To ensure that the capacity licensing details are accurate, you must upgrade SnapProtect Version 9 virtualization clients to Version 10. After the upgrade, make sure to run full backup jobs (not synthetic full).
  • Logical volume manager (LVM) metadata processing for volumes encrypted using BitLocker is currently not supported. Decrypting contents of such volumes may not be feasible during backup because decryption requires a recovery password or a decryption key. Because metadata collection for the volume fails, the reported guest size for virtual machines with encrypted volumes may be incorrect and a file-level browse operation for the encrypted volume cannot display file information.

Verifying Backup Job Data for Virtual Machines

To get a detailed listing of backup job data for each virtual machine, you can log in to the CommServer host using qlogin and run the following stored procedure on the CommServe database:

qoperation execscript -sn QS_CLAGetVSADetails –cs commserve_host_name –file file_name -format csv

The resulting output shows the size of the latest backup job for each virtual machine. The size value is the guest size for the VM, or the used space if guest size is unavailable; the size value for all VMs is used in the overall capacity licensing calculation.

The output also shows which license category each VM counts against, and provides instance, backup set, subclient, and job information for each VM.

How can a virtual machine be restored in a disaster recovery scenario?

Both the primary and disaster recovery sites must include a MediaAgent and VSA proxy.

Configuration

Perform the following steps to configure the proxy and subclient for backups:

  1. At the instance level, add the proxy for the primary site:
    1. In the CommCell Browser, navigate to Client Computers | <Client> | Virtual Server.
    2. Right-click VMware and select Properties.
    3. Click the Proxies tab and click Add.
    4. On the Select Clients / Client Groups dialog, select the proxy for the primary site and click Include.
  2. Configure the subclient:
    1. In the CommCell Browser, navigate to Client Computers | <Client> | Virtual Server | <BackupSet>.
    2. Right-click the subclient and select Properties.
    3. Click the Advanced Options tab and click Add.
    4. On the Select Clients / Client Groups dialog, select the proxy for the primary site and click Include.
    5. On the Storage Device tab, select an appropriate storage policy.

      The primary copy for the storage policy specifies the primary site backup location, and the secondary copy specifies a backup copy location that is used for disaster recovery.

Recovery

To recover from the disaster recovery site:

  1. Right-click the subclient and select Browse and Restore.

    Leave the Full Virtual Machine option selected on the Virtual Server tab of the Restore Options dialog.

  2. Click the Advanced Options tab and choose the following options:
    1. Select the Browse from copy precedence option and change the value to 2.
    2. For the Use MediaAgent field, select the VSA proxy for the disaster recovery site.
  3. Click View Content.

    If the backed up VMs are not displayed, you may need to close and reopen the CommCell Console.

  4. Select the virtual machine to be restored in the left pane.
  5. Click Recover All Selected.
  6. On the General tab of the Restore Options for All Selected Items dialog:
    1. Clear the Restore in place check box.
    2. For the Destination client field, select the VSA proxy for the disaster recovery site.
    3. Click Change to specify a different vCenter.
    4. On the resulting dialog, enter the name of the vCenter to which the virtual machine should be restored and provide the vCenter credentials, then click OK.
    5. Click in the ESX Server column and click the ... (browse) button to select the destination host and datastore, then click OK.
    6. Select the Unconditionally overwrite VM with the same name option.

      If the Unconditionally overwrite VM with the same name option is used when restoring a virtual machine that has independent disks, the independent disks and their VMDKs are removed from the datastore and are not restored.

  7. Click OK to perform the restore operation.

Related Topics

For more information, see Disaster Recovery - Virtual Server Agent for VMware.

Why is my backup data showing volume numbers instead of drive letters?

If hard disk filtering was used for the backup and the drive that contains the operating system was excluded from the backup, the backup is unable to obtain information about drive letters. You can still browse and restore backed up files on the volumes that were backed up.

Can we perform load balancing across datastores or volumes?

When backup jobs are run for multiple virtual machines (VMs), VMs are backed up sequentially, with each VM backup on a separate job stream. The number of simultaneous job streams can be limited through configuration for the storage policy and subclient, and by the number of available data paths for a datastore or volume where backup data is being written.

By default, the next VM to be backed up and assigned to a job stream is selected randomly from the list of VMs that remain to be backed up. This default selection can lead to performance issues when most of the backup jobs are writing to the same datastore or volume.

For streaming backups (including Backup Copy for SnapProtect), you can perform load balancing across datastores and volumes by setting nGetNextVMMethod on the Virtual Server Agent (VSA) proxy that performs the backup. When this parameter is set to 1, SnapProtect checks activity on datastores and volumes sequentially, based on each VM's primary datastore or volume, and selects the next virtual machine for backup for the datastore or volume with the smallest number of VMs being backed up by the current job.

To set the nGetNextVMMethod option:

  1. From the CommCell Browser, go to Client Computers | <VirtualizationClient>.
  2. Right-click the VSA proxy and select Properties.
  3. On the General tab of the Client Computer Properties dialog, click Advanced.
  4. On the Advanced Client Properties dialog, click the Additional Settings tab.
  5. Click Add.
  6. Add the following entry:
    • Name: nGetNextVMMethod
    • Category: Virtual Server
    • Type: Integer
    • Value: 1 (to perform load balancing across datastores and volumes)
  7. Click OK to save the additional setting.
  8. Click OK twice more to save the advanced client properties and the client properties.

Do backups take a snapshot of virtual machine memory?

Virtual Server Agent backups do not snapshot VM memory during backups.

If the Quiesce Guest File System and Applications option is configured in the Backup Options for the subclient, the guest file system and applications are quiesced before taking a hardware snapshot for the backup to ensure data consistency.