QSnap/Open File Handler (OFH) for the Image Level ProxyHost iDataAgent

Choose from the following topics:

• Overview
• Configuration
• Required Software
• Hardware and Software Considerations

Related Topics:

• QSnap
• Open File Handler (OFH)
• Snapshots
• Support Information - Image Level ProxyHost Data Types

Overview

The use of QSnap or OFH ensures that file system metadata remain unchanged, and therefore consistent, during the backup operation. QSnap or OFH is fully integrated with Image Level ProxyHost, creating a software snapshot during the Scan phase of the backup. Thus, all of the components necessary for basic Image Level iDataAgent functionality are available without requiring specialized hardware. For improved performance and flexibility, and enhanced features, you can supplement the Image Level ProxyHost iDataAgent and QSnap or OFH with a hardware-based snapshot implementation.

Configuration

The following must be done before using the Image Level ProxyHost iDataAgent with QSnap or OFH:

1. Verify that the computer in which you wish to install the software satisfies System Requirements for the Image Level ProxyHost and File System iDataAgents.
2. Install the required software.
3. Review the Hardware and Software Considerations.
4. Configure subclient(s) and content. See Subclients - SAN iDataAgents for more information.
5. Create PreScan and PostBackup batch files. It is important to note that these batch files will have to be customized for each individual environment.

   It is not necessary to quiesce the server for a file system backup with Image Level ProxyHost, and thus, no need of calling CVSnaptool from a pre-scan batch file.

   We recommend that you test batch files before associating them with any subclients.

   For specific information on the PreScan and PostBackup processes, see the Resource Pack for sample batch files.

Required Software

Windows

The following must be installed on the production server:

• Windows File System iDataAgent
• Image Level iDataAgent
• Image Level ProxyHost iDataAgent
• QSnap or Open File Handler (OFH)

The following must be installed on the backup host:

• Windows File System iDataAgent
• Image Level iDataAgent
• QSnap or OFH

Note: OFH is installed automatically during installation of the Image Level iDataAgent.

All configuration for Open File Handler (or QSnap) needs to be done only on the host machine’s Image Level iDataAgent.

Unix

The following software must be installed on the production server:

• Unix File System iDataAgent
• Image Level iDataAgent
• Image Level ProxyHost iDataAgent
• Unix QSnap driver (installed automatically during installation of the Image Level iDataAgent)

The following must be installed on the backup host:

• Unix File System iDataAgent
• Image Level iDataAgent
• QSnap (installed automatically during installation of the Image Level ProxyHost iDataAgent)

For more information and procedures, see Deployment - Image Level ProxyHost iDataAgent.

Hardware and Software Considerations

General

• Verify that the backup host is properly configured and connected to the S-Vol.

Windows

• When working with file systems other than NTFS, you must set an alternate COW Cache location on an NTFS volume. Increase the maximum size of the QSnap/OFH COW Cache to accommodate your disk configuration and usage. See Windows COW Cache for more information on COW Cache configuration.
• After installation, it is highly recommended that you configure persistence for the volumes you are protecting. See Persistence for more information.

UNIX

• The COW Cache mount point is selected at the time of installation. See Unix COW Cache in the Overview - QSnap page for more information on supported COW cache configurations.
• After installation, you must configure CXBF devices with Volume Explorer. See CXBF Devices in the Overview - QSnap page for more information.
• If you did not enable Unix QSnap when you installed it, see Enabling/Disabling the Snapshot License on Unix Platforms in the Overview - QSnap page.

Configure Extent Size

Unlike a File System iDataAgent, the Image Level ProxyHost Agent backs up extents on the source drive. The extent size is initially set to 2 MB, effectively dividing the source volume. (On Unix, the GUI will display 4096.) In most cases, this 2MB default size is best for performance.

But there may be reasons for increasing or decreasing extent size to improve performance. Keep in mind that a 2MB extent with just 10KB of data is backed up entirely, including its empty blocks of data. Again, this will work fine in most cases, but factors such as the state of data fragmentation on the source, network bandwidth, and server speed should be considered. These factors, along with extent size, can impact both the speed and the size of backups.

If performance is inhibited because of extent size issues, contact your software provider for more information about tuning your software for maximum performance.

Also consider the following implications of changing extent sizes:

• For Image Level ProxyHost on Linux or Solaris, the extent size can only be changed when the CXBF device is configured. Thus, to modify the extent size of an existing CXBF device, you must first deconfigure the CXBF device and then configure again.
• When configuring a CXBF device from Volume Explorer for Image Level ProxyHost on Linux, the value entered must be a power of 2. Using a value which is not a power of 2 will cause the CXBF device configuration to fail. By default, the value is 4096; examples of acceptable values would be 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, etc.

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