VSS for the ProxyHost iDataAgent

Overview

The ProxyHost iDataAgent can be implemented in conjunction with the VSS Enabler to conduct backup operations using a VSS Hardware Provider. ProxyHost uses the snapshot to back up large amounts of data without using production server resources. Because the backup does not occur on the production server, resources on the production server are not affected by this operation.

VSS Hardware Providers

VSS Hardware providers allow you to create shadows without imposing a load on the local client, or production server. For the purposes of VSS, the snapshot is referred to as a shadow. Furthermore, an option to make the shadow transportable has been provided, which allows you to mount, or import, the shadow on another client. If a shadow is not marked as transportable, you will not be able to mount the shadow.

When using VSS, the system will use the default provider to create the shadow. If you have installed a hardware provider, this becomes the default provider (VSS will use the hardware provider in place of Microsoft Shadow Copy. The Microsoft Software Shadow Copy provider cannot be used for snapshots if you have a VSS hardware provider installed. The VSS hardware provider will have a higher precedence than the Microsoft Software Shadow Copy provider and so QR Volume creation or backups with the Shadow Copy Provider will fail.

If there are multiple hardware providers residing on the same machine, note that not all hardware providers will support the same volumes. For example, the EMC provider will only support disks on the CLARiiON, the HDS provider will only support HDS disks, etc. VSS determines if a supports the volume to be snapped.

VSS Hardware Provider Environment - ProxyHost

The diagram that follows shows a sample ProxyHost configuration in a VSS Hardware Snapshot Provider environment.

Data from the production server is snapped by the VSS Hardware Provider; this snapshot is referred to as a shadow. The shadow is imported to the Backup Host, and ProxyHost begins the backup. When the backup completes, the shadow is deleted.

The ProxyHost iDataAgent is installed on the production server only. The same File System iDataAgent is installed on both the production server and the backup host. In addition, the VSS Enabler is installed on the production server and backup host.

During a ProxyHost backup, the following sequence of events takes place:

The ProxyHost iDataAgent starts a backup operation.
The PreScan process creates the transportable shadow.
The shadow is imported to the backup host.
The shadow is backed up through the backup host.
During the PostBackup process, the shadow is deleted.

Configuration

The following must be done before creating VSS Hardware shadows.

Verify that the production server and Backup Host meet the System Requirements.
Install the required software. Note that you can de-select QSnap during the install if you will be using VSS exclusively.
Review the VSS Considerations.
Your hardware provider may require some configuration before use. This may include creating a cache LUN, setting up snap or clone groups, etc. Consult your hardware provider for any necessary steps to set up a snap environment.
You must create the following two Registry keys:
- nTRANSPORTABLEFLAG must be created and set to a value of 1 on both the source and destination hosts.
- SLOCALBCDBASEPATH must be created on the source host (and set to the path to which you will store the BCD files.
Create a Source-Destination Mapping File for ProxyHost.
Create the subclient. See Create a New Subclient and Configure Subclient Content for instructions. Note the following:
- Only volumes that are owned by the hardware provider should be included as subclient content.
- VSS shadows taken together are treated as a single unit. Actions taken on one shadow in a subclient will be applied to all shadows in the subclient. (e.g., if shadows are created for the F: drive and the G: drive through a single subclient, and one of the shadows is imported, then the other will also be imported automatically).
- Configure PreScan and PostBackup scripts. For specific information on the PreScan and PostBackup processes, see the Resource Pack for sample batch files.

Required Software

The following software must be installed on the production server:
- ProxyHost iDataAgent
- Quick Recovery Agent
- Windows File System iDataAgent
- VSS Enabler
- For Exchange 2003:
  - Exchange 2003
- For SQL Server:
  - SQL Server with SP1 or higher
The following software must be installed on the Backup Host:
- Quick Recovery Agent
- Windows File System iDataAgent
- VSS Enabler

For more information and procedures, see Deployment - Quick Recovery Agent and Deployment - ProxyHost iDataAgent.

VSS Considerations

Before using VSS, review the following information:

Windows 2003 service pack 1 is required to be installed on both source and destination machine.
VSS hardware providers create snapshots at the LUN level, not the partition level. It is recommended that each LUN have only one partition. Using LUNs with multiple partitions may create unexpected results.
Transportable shadows can only be deleted after they have been imported. If you attempt to delete a transportable shadow that has not been imported, it will be automatically imported to the default import host before deletion.
You can create a VSS clone by creating the nUsePlexMode registry key and setting the DWORD value to 1. See your hardware provider for setting up the environment. Currently, ProxyHost and the QR Agent support clones using the EMC VSS CLARiiON provider.
You cannot create multiple VSS shadows of a source volume in a single Source-Destination mapping file. Even if you specify different destination mount points, any subsequent shadows of the same source will overwrite the shadow created before it. You can, however, use a different Source-Destination mapping file to create another shadow of the source volume to a different mount point.
When restoring data that was backed up from Exchange using the Log truncation feature in combination with a VSS hardware provider snapshot, and the *.chk file was located on a different volume, it must be manually deleted before attempting to mount Exchange Stores after a restore procedure. This will ensure that you will not have a *.chk file which does not match the logs and database being restored, and thus be unable to bring up the Exchange Stores after the restore. Exchange will create a new *.chk file based on the log you restore.
Example:
The System path location of the storage group is: C:\Program Files\Exchsrvr\mdbdata, and not on the volume where the snapshot was taken.

License Requirement

To perform a data protection operation using this Agent a specific Product License must be available in the CommServe^® Server.

Review general license requirements included in License Administration. Also, View All Licenses provides step-by-step instructions on how to view the license information.

Enabler Licenses

VSS Hardware snapshot also requires a license for the VSS Enabler.