Limits for the server database size and peak client sessions

IBM tests the IBM Spectrum Protect server to a specific database size and peak number of concurrent client sessions. However, you must consider the tested values along with other operational factors in your specific environment. Experiences that are reported by other users are also helpful.

Database size

Testing shows that databases with utilization as much as 4 TB are possible.

The practical limit for the database size depends on the performance characteristics of the server system and the time that is required to back up or restore the database. For many users, a 1 - 2 TB server database allows completion of database backup and database restore operations in a time that fits their maintenance window.

Consider deploying another server if the following conditions occur:
  • Performance degrades to an unacceptable level as the database grows
  • The time that is required to complete server maintenance such as database backup exceeds the total window of time for server maintenance
When you add a server, either balance the existing workload across the servers, or assign any new workload to the new server.

Peak number of client sessions

Testing shows that the IBM Spectrum Protect server can handle up to 1000 concurrent client sessions. If this value is exceeded, depending on memory or other system limitations, the server performance might degrade or operations might become unresponsive.

The actual number of concurrent sessions where performance problems arise depends on the resources that are available to the server. What the sessions are doing also influences the practical limit on sessions. For example, sessions that move data have a larger effect on the amount of I/O to the target storage pool compared to incremental backup sessions that mostly send queries without sending many files. Also, sessions that perform client-side deduplication drive more I/O to the server database than other sessions.

To reduce the peak-session workload, it might be appropriate to deploy another server or to adjust client scheduling.

Set the MAXSESSIONS server option no higher than the tested limit of 1000. Setting the maximum number of sessions higher than necessary uses extra RAM on the server system, but might not have a significant impact.