mbobjrefreshthresh client option

For example, when the number of IBM Storage Protect objects exceeds this value, the megablock is refreshed. This action means that the entire 128 MB block is backed up to the IBM Storage Protect server and is represented as a single IBM Storage Protect object.

Before you set a value for the mbobjrefreshthresh option, review the following information:

Preferred setting

The preferred value is the default, 50. When the number of IBM Storage Protect objects that are needed to describe a 128 MB megablock for a virtual machine guest disk exceeds this value, the entire megablock is refreshed.

If you are backing up to a tape storage pool on the server, you might decrease this value so that megablock refreshes occur more often. This way, the data that was backed up for each virtual machine guest disk is more likely to be collocated on tape volumes. This setting might improve restore performance in such cases.

Effects on performance

When a megablock is refreshed, the objects that were used to represent the megablock area in previous backups are expired. This option can affect the quantity of data that is copied to the IBM Storage Protect server and the server database-related processor utilization during incremental forever backups.

Potential trade-offs for this setting

Setting this option close to its maximum value of 8192 can result in sending less data to the IBM Storage Protect server during an average incremental forever backup operation. However, the number of database entities that the IBM Storage Protect server must track increases. This result can increase server processor utilization during incremental forever backups by a small degree.

Setting this option close to its minimum value of 2 can result in marginal database processing savings during incremental forever backups. However, the quantity of data that is copied to the IBM Storage Protect server might be higher and might approach the size of a full backup.