About AdvancedDisk preferred or required read servers

When you configure a storage server, you can specify that you want it to be preferred or required for restore jobs. You also can specify whether a server should be required for the read side of duplication jobs. These attributes can help manage the restore and the duplication traffic.

Table: Preferred or required read server descriptions

Server attribute	Description
PrefRestore	The server is preferred for the read side of restore operations. You can configure more than one server as preferred for restore. If you configure preferred for restore but not required for restore, NetBackup considers preferred storage servers for jobs first. If none are available, NetBackup considers any configured storage server. Normal NetBackup load balancing occurs among all storage servers marked PrefRestore.
ReqRestore	The server is required for the read side of restore operations. You can configure more than one server as required for restore. If you configure required servers for restore but not preferred servers, jobs queue until a required server is available to execute the job. Other servers are never considered for restore jobs. Normal NetBackup rules for job retry apply. If you configure both preferred and required storage servers and a required server is not available, NetBackup considers preferred servers for jobs. If none are available, jobs queue until a required or preferred server is available. Other servers are never considered for restore jobs. Normal NetBackup load balancing occurs for all required servers. Load balancing does not occur between the required and preferred servers.
ReqDuplicate	The server is required for the read side of duplication operations. You can configure more than one server as required for duplication. If any server is configured as required for duplication, NetBackup considers only required for duplication servers for jobs. If a required server is unavailable, jobs queue until a required server is available to execute the job. Normal NetBackup rules for job retry apply. Required for duplication also applies to storage server allocation for synthetic backup operations.

Server attribute

Description

PrefRestore

The server is preferred for the read side of restore operations. You can configure more than one server as preferred for restore.

If you configure preferred for restore but not required for restore, NetBackup considers preferred storage servers for jobs first. If none are available, NetBackup considers any configured storage server.

Normal NetBackup load balancing occurs among all storage servers marked PrefRestore.

ReqRestore

The server is required for the read side of restore operations. You can configure more than one server as required for restore.

If you configure required servers for restore but not preferred servers, jobs queue until a required server is available to execute the job. Other servers are never considered for restore jobs. Normal NetBackup rules for job retry apply.

If you configure both preferred and required storage servers and a required server is not available, NetBackup considers preferred servers for jobs. If none are available, jobs queue until a required or preferred server is available. Other servers are never considered for restore jobs.

Normal NetBackup load balancing occurs for all required servers. Load balancing does not occur between the required and preferred servers.

ReqDuplicate

The server is required for the read side of duplication operations. You can configure more than one server as required for duplication.

If any server is configured as required for duplication, NetBackup considers only required for duplication servers for jobs. If a required server is unavailable, jobs queue until a required server is available to execute the job. Normal NetBackup rules for job retry apply.

Required for duplication also applies to storage server allocation for synthetic backup operations.

Only the media servers that are configured in the storage unit are considered for jobs. Therefore, if you configure a subset of the disk pool media servers in a storage unit, NetBackup selects from those servers only.

If you use the preferred or required restore or duplication attributes for a storage server, the following may occur:

A restore operation uses a storage server that does not have a PrefRestore or ReqRestore attribute. Reasons may be as follows:
- The destination disk pool does not include a storage server with a restore or a duplication attribute.
- A preferred or required storage server cannot be used because it is unavailable (NetBackup considers it DOWN).
A restore or a duplication operation is queued.

The reason may be that a preferred or required storage server cannot be used because it is unavailable (NetBackup considers it DOWN).

If you do not configure preferred or required restore servers, NetBackup uses normal criteria to select a media server for restore or duplication. (That is, if you configure more than one storage server.)

Information about how NetBackup balances storage unit and media server load is available.

See Maximum concurrent jobs setting.

You can use preferred or required restore servers rather than the Media host override host property.

Information about the Media host override property is available.

See General Server properties.

To enable preferred or required servers for restore or duplication, do the following:

Upgrade the NetBackup master server and the NetBackup EMM server to NetBackup 6.5.2 or later. (Normally, the master server and the EMM server are on the same computer.)
Optionally, to enable command-line support on media servers, upgrade the media servers that are used for AdvancedDisk operations to NetBackup 6.5.2 or later.

You do not have to upgrade the media servers. You can configure and manage the restore and the duplication storage servers by invoking the commands on the master server.