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Frequently Asked Questions - SnapProtect for Microsoft Hyper-V

Table of Contents

How does the SnapProtect backup operation work?

When you run a SnapProtect backup operation, the SnapProtect software performs the operations listed below in the following sequence of events:

Create Snapshot on the Source

This event includes the following operations:

  1. Device detection based on subclient content.

    This operation gathers information from local volume managers, multipath devices and physical disks (including partitions). For example, information on UUIDs is retrieved from a local volume manager.

  2. Take snapshot of detected devices

    This operation invokes the snapshot functions from the file server and creates the snapshot. Once created, SnapProtect records the snapshot in the CommServe database along with metadata, which includes information about local volume managers, multipaths and physical disks.

Mount Snapshot on Proxy

This event includes the following operations:

  1. Map LUNs to the MediaAgent

    This operation invokes the file server functions to map clone devices to the proxy MediaAgent.

  2. Recreate Storage Hierarchy

    Based on the metadata collected during device detection and snapshot creation, SnapProtect recreates the storage hierarchy as follows:

    • Devices are rescanned at the operating system level in order to allow the proxy to see the snapshot LUNs.
    • For each device detected on the source, SnapProtect checks the partitions to determine if the device is accessible or if it is a multipath device. If it is a multipath device, then the operation fails as partitions on multipath are not supported. However, if it is not a multipath device, then the software will keep parsing the device name to retrieve the partition information.

      When a partition number is detected, it is appended to the device name of the LUN. If no partition number is found, the full device name is used.

    • If required, the hierarchy of the local volume manager is recreated based on the metadata collected during device detection and snapshot creation.
    • File systems (LUNs and multipath disks) are mounted on the detected devices. Logical volumes are mounted in the case of logical volume managers.
    • Index is created and the software moves the data to the media.

What provisioning policies can I use?

Provisioning Policies are optional to use. During the creation of the secondary snapshot copy, the following Provisioning Policies are automatically created and available for selection in the CommCell Console:

  • SnapProtect_RAID-DP
  • SnapProtect_Dedupe
  • SnapProtect_Mirror_Destination

If you need to create your own provisioning policy, ensure it is defined with the following naming convention in the OCUM server:

SnapProtect_<provisioning_policy_name>

where "SnapProtect_" is the prefix required for the provisioning policy to be available in the SnapProtect software.

What happens when a Vault/Mirror copy is created?

During an Auxiliary Copy job, a new dataset is created or an existing dataset is modified with new data members, as explained in the following flow of events:

  1. When the SnapProtect software assigns data to the service catalogue, a new baseline transfer may have started in the OnCommand Unified Manager (OCUM) server.
  2. The Auxiliary Copy job details display its status as the baseline transfer is in progress.
  3. Once the baseline transfer is completed, the SnapProtect software adds the snaps to the backup list, and the backup starts with the OCUM.
  4. If SnapMirror is the destination copy, then the SnapProtect software sends a command to update the mirror.

    The OCUM job is monitored and marked as completed/failed depending on the OCUM job status.

How are snapshots copied during a backup copy operation?

The snapshots are copied to media in a sequential order. If you wish to perform an inline backup copy operation and a previously selected snapshot has not been copied to media, the current SnapProtect backup job will complete without creating the backup copy and you will need to create an offline backup copy for the current backup.

What should I take into account when using retention by number of jobs?

Configuring a storage policy or snapshot copy with job based retention is recommended for File System and File System like Agents, and not for Database Agents.

Review the following scenarios if you are using the retention by number of jobs configuration:

  • During a browse operation, deleted files may be displayed for recovery. If the jobs containing these files are pruned by the retention criteria, the deleted files will be irrecoverable.
  • You may need to manually delete jobs from deconfigured clients. These clients will continue to retain the old jobs since new jobs will not run again on them.
  • When you associate a new storage policy to a subclient, it is important to perform a full backup operation in order to be retained by the new storage policy. The old storage policy will continue to retain the old jobs until you manually delete them.

What UTF setting should be used for volume language?

To successfully browse and restore files on a NetApp file server that contain Unicode characters, use the UTF-8 setting for volume language. Consult with NetApp for implications of changing volume language.

Is multi instancing supported?

No. Multi Instancing is not supported for SnapProtect backup.

Can I use Media Explorer to restore data?

No. You cannot use Media Explorer to restore data. However, you can use the Media Explorer to restore SnapProtect backup data from the backup copy.

How do I determine the number of streams to be used for a restore operation from an SnapProtect backup?

For DB2, SAP for Oracle, and Oracle iDataAgents, when restoring from a snapshot using file system, the number of streams depends on the number of mount points used for the restore operation. Similarly, when restoring from a backup copy using file system, the number of streams depends on the number of media groups used for the restore operation.

How does SnapProtect select target devices during Clone/Snap operations?

When you configure an storage device using Array Management in the CommCell Console, the Device Group text box defines the target device group where SnapProtect will move the source and target devices during SnapProtect backup operations. This option does not specify the source device group (from where a device should be found during Snap/Clone operations).

The following table explains the default behavior for selecting a Snap or Clone target device:

Scenarios based on Array Management Options Target device is selected from... Source and Target devices are moved to...
Device Group is not specified and Use devices only from this device group is not checked Any device in the array CV_PROTECTION_GROUP device group
Device Group is not specified but Use devices only from this device group is checked CV_PROTECTION_GROUP device group CV_PROTECTION_GROUP device group
Device Group is specified but Use devices only from this device group is not checked Any device in the array The device group specified in Device Group
Device Group is specified and Use devices only from this device group is checked The device group specified in Device Group The device group specified in Device Group

Can I back up pass-through devices in a virtual machine using SnapProtect?

Yes. You can use the File System Agent and  SnapProtect to back up pass-through devices if the following conditions are satisfied:

  • The MediaAgent that is used for the SnapProtect backup is installed on a physical computer and not on a virtual machine.
  • The File System Agent is installed on the virtual machine that is being backed up.

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 Backup license count (depending on the storage policy configuration).
  • Backup copy operations are included in the Backup license count.
  • Archived VMs are included in the Archive license count.
  • SnapProtect backups are included in the 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 Backup license.

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.

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 20 GB used on a 100 GB disk, 20 GB 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.

For more information about virtual machine sizes, see Size Measures for Virtual Machines.

Verifying Backup Job Data for Virtual Machines

To review backup information for virtual machines, generate a VM Backup Report.

Alternatively, you can log in to the CommServe 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.