GridStor® (Alternate Data Paths) - Best Practices

Configuring LAN-Free Operations and Sharing the Index on MediaAgents

For LAN-free clients, do not enable the When Resources are Busy option to choose an alternate data path. This will ensure LAN free operations, wherever possible.

It is not necessary to share the index on MediaAgents with LAN-free data paths. If any additional alternate data path on the LAN is added to the storage policy, the index will be pulled from the last seen MediaAgent in the data path list.

Make sure all MediaAgents used in the data paths of each storage policy use:
  • Either local index cache

    This is a recommended configuration if MediaAgents will always be available and may not go offline at all.

  • Or the same shared profile

    This is not a recommended configuration but if there are chances of MediaAgent going offline or becoming unavailable, then you may use this option.

Combination of data paths of MediaAgents using local index cache and shared profile will not work.

Avoiding Data Fragmentation by Using Fewer Storage Policies

Create and use fewer storage policies because a large number of storage policies will result in the fragmentation of data on media. Consider the following:

  • Control data retention by creating copies within the Storage Policies. (As opposed to creating many storage policies with different retention periods.)
  • Consolidate each Client's data by creating a storage policy copy by associating subclient in the Association tab. See Assigning CommCell Entities to a Storage Policy Copy for instructions.

Deconfiguring a Library

Before you deconfigure a library, verify and ensure that none of the Storage Policy Copy's default data path points to the library. (See View the Storage Policies Accessing a Library for step-by-step instructions on how to view the storage policies associated with a library.) If necessary, set an alternate data path as the default data path before deconfiguring the library.

If you have a storage policy copy with no default data path, use Change Data Path option to migrate the storage policy to point to another data path. See Change Data Path for more information.

NAS Load-Balancing

NAS Load-Balancing - in addition to the resource load balancing that the Alternate Data Paths feature provides, NAS can be configured to load balance the processing tasks associated with backup, restore, and auxiliary copy jobs, which normally run on a single client machine, to spread the processing among different MediaAgent.

Data paths for NAS attached libraries can only be added if the MediaAgent used in that data path also has the File System iDataAgent installed on that computer.

Using Alternate Data Paths to Back Up the Microsoft Virtual Server

If the MediaAgent software is installed in the cluster server, configure a disk library to backup the data.

If you want to configure a tape library, install the MediaAgent software on the physical computer.

Add a data path which uses this MediaAgent, Library, Drive Pool and Scratch Pool combination to the Storage Policy used to  backup the cluster server.  (See Add a Data Path to a Storage Policy Copy for more information.)

Assign this as a high priority data path in the subclients used to backup the cluster server. (See Assign Priorities for Subclient Data Paths for more information.)

Checking Media Compatibility While Changing Data Paths in Libraries and Drives

When you change the data paths make sure that the libraries and drives in the source and destination library are compatible. Specifically, the destination library must be capable of reading the bar codes on the media for which you have changed the data path. See the library manufacturer's documentation for compatible bar codes.

Make sure that the firmware of the source and target library can read the barcodes of media exactly the same way.

Ensuring Compatibility and Availability of Drive Pools

Ensure that the drives of the destination drive pool are compatible with the recording format and hardware type of the migrating media.

  • An example of recording format incompatibility: Data paths can be changed from DLT 4000 drives to DLT 7000 drives as tapes written by DLT 4000 drives can be read in DLT 7000 drives. However, data paths cannot be changed from DLT 7000 drives to DLT 4000 drives, as tapes written by DLT 7000 drives cannot be read in DLT 4000 drives.
  • Another example of hardware type incompatibility: DLT tapes cannot be inserted into AIT or Mammoth drives or vice-versa.
  • Media from an NDMP drive pool can only be changed to another NDMP drive pool. (An NDMP drive pool is one containing drives that are attached to a NAS filer rather than to a MediaAgent.) Data Paths cannot be changed from NDMP to non-NDMP libraries.

Also confirm that there are sufficient drives in the destination drive pool to accommodate all of the streams of the copy for which the data paths are changed. For example, a drive pool should contain at least three drives to accommodate a three-stream copy.

Changing Data Paths in Compatible Libraries and Drives

It is possible to change the data paths for compatible libraries to stand-alone libraries and vice-versa, and between compatible stand-alone drives to stand-alone drives.

Exporting Media When Changing Data Paths Between Libraries

When you change the data paths from one library to another, you must physically remove all of the media from the source library and insert them into the destination library. It is strongly recommended that you export such media from the source library and immediately import them in the target library. If you want to export all the media from the library, you can use the Mark Media Exported option from the library level. For more information, see Export Media.

Once you change the data path and import the media in the target library, subsequent backup operation, which uses these media, will mark active media as appendable and use a new media.

Configuring Alternate Data Paths for Existing Libraries

When multiple MediaAgents share the same library (SAN DDS, or direct-attached shared library configurations) the system can automatically add the alternate data paths for each of the storage policies, when this option is enabled. As each of these data paths (MediaAgent, Library, Drive Pool and Scratch Pool) use the same resources, additional index cache configuration is not required. In addition, the criteria for using the alternate data path (described in the following section) must also be specified.

Using Alternate Data Paths for a Shared Library Configuration

If both the default and alternate data paths are configured to use the same library, as a result of a shared library configuration (configured as a SAN DDS library or direct-attached shared library) the MediaAgent will automatically use the appropriate Assigned media for the data protection operation.

If the default and alternate data paths are configured to use different libraries, the MediaAgent, marks the previously used Assigned media as Appendable and uses a new media from the library associated with the alternate data path.

Such Appendable media can be re-used in the library by enabling the Use Appendable Media option in the Library Properties dialog box associated with the library.