QSnap for the Image Level ProxyHost iDataAgent
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Overview
Configuration
Required Software
Hardware and Software Considerations
The use of QSnap ensures that file system metadata remain unchanged, and
therefore consistent, during the backup operation. QSnap 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 with a hardware-based
snapshot implementation.
The following must be done before using the Image Level ProxyHost
iDataAgent with QSnap:
- Verify that the computer in which you wish to install the software
satisfies
System Requirements
for the Image Level ProxyHost and File System
iDataAgents.
- Install the required software.
- Review the Hardware and
Software Considerations.
- Configure subclient(s) and content. See
Subclients - SAN
iDataAgents for more information.
- 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.
Windows
The following must be installed on the production server:
- Windows File System iDataAgent
- Image Level iDataAgent
- Image Level ProxyHost iDataAgent
- QSnap
The following must be installed on the backup host:
- Windows File System iDataAgent
- Image Level iDataAgent
- QSnap
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- QSnap is installed automatically during installation of the Image Level
(or Image Level ProxyHost)
iDataAgent.
- For a clustered
environment, first install the Windows File System
iDataAgent
and QSnap on the physical nodes, and then reboot the nodes. After
rebooting the nodes, install the Image Level ProxyHost
iDataAgent
and the Image Level iDataAgent
on the virtual node. (The Windows File System iDataAgent
is automatically selected when you install the Image Level
iDataAgent.)
- All configuration for QSnap needs to be done only on the host
machine’s Image Level iDataAgent.
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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
(or Image Level ProxyHost) 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 (or Image Level ProxyHost) iDataAgent)
For more information and procedures, see
Deployment - Image Level
ProxyHost iDataAgent.
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 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.
- When you add a volume to a subclient content, it is
automatically configured as a CXBF device. See
CXBF Devices in the Overview -
QSnap page for more information.
Unlike a File System iDataAgent,
the Image Level ProxyHost Agent backs up extents on the source drive. The extent
size is initially set to 512KB for Windows.
For
Unix, the default extent
size is 2MB (the Unix GUI will display 4096 because 4096 x 512 bytes equals 2MB). In most cases, the default
extent size effectively divides the source volume and is best for
performance.
But there may be reasons for increasing or decreasing extent size to improve
performance. Keep in mind, for example, that a 512KB 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 for some
reasons the extent size is required to be changed, see
Change extent size
for Backup Applications for
more information on changing extent sizes.
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:
- Backup extent size must be uniform across source and destination
computers.
- In a clustered environment, all the physical nodes must have the same
Backup extent size.
- Backup extent size should not be larger than the size of the volume.
- 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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