Mbpctrefreshthresh

The mbpctrefreshthresh (megablock percentage refresh threshold) option is a number defining a threshold. When the number of Tivoli® Storage Manager percentage of objects that are needed to describe any 128 MB megablock exceeds this value, the entire megablock is refreshed and the objects that were used to represent this area, in previous backups, are expired.

When you backup a virtual machine, data is stored on the Tivoli Storage Manager server in 128 MB units, called megablocks. If an area on the production disk changes and a new incremental backup is performed, a new megablock is created to represent the changes that were made to the previously backed up data. Because a new megablock can be created with each incremental backup, eventually the megablocks can adversely affect the performance of the Tivoli Storage Manager database, and therefore, adversely affect the performance of most Tivoli Storage Manager operations.

Use this option when estimating the amount of additional data that is backed up for each virtual machine. For example, when a 128-MB block of a production disk changes more than the percentage specified, the entire 128-MB block is copied to the Tivoli Storage Manager server. The block is represented as a single Tivoli Storage Manager object.

Supported clients

Linux operating systems Windows operating systems This option is valid for clients that act as data mover nodes that protect VMware virtual machines. You must be licensed to use Tivoli Storage Manager for Virtual Environments: Data Protection for VMware to use this option.

Windows operating systems This option is valid for clients that act as data mover nodes that protect VMware virtual machines or on clients that protect Microsoft Hyper-V virtual machines. You must be licensed to use Tivoli Storage Manager for Virtual Environments: Data Protection for VMware, or Tivoli Storage Manager for Virtual Environments: Data Protection for Microsoft Hyper-V to use this option.

Options file

Specify this option in the client options file.

Syntax


                       .-50------.   
>>-MBPCTREFRESHTHRESH -+---------+-----------------------------><
                       '-integer-'

Parameters

The minimum value you can specify is 1 percent, the largest value is 99 percent; the default is 50 percent.

Examples

Set this option to trigger a megablock refresh when 50 percent (or more) of the objects in a megablock on a production disk have changed:

		MBPCTREFRESHTHRESHOLD 50