Data Domain Best Practices


All Data Domain systems

All Software Releases



This document contains some general configuration and usage recommendations that will help get optimum performance out of your Data Domain system, with minimal problems.



Although Data Domain systems offer numerous configuration and usage options, some combinations of settings may impair performance or introduce usage problems, while others improve performance.




  • Attempt to keep the Data Domain system less than 85% full.  Filesystem Cleaning and other operations will be faster and more efficient when the system has enough available disk to perform these important tasks.
  • Try to schedule Filesystem Clean (also known as Garbage Collection or filesystem cleaning) to run during times when active backups are not running, to avoid resource contention and extended cleaning times.
  • The default Filesystem Clean schedule is sufficient in the vast majority of environments. Consult the document "Scheduling Cleaning on a Data Domain System: Best Practices" to better understand this process. If you still feel there is reason to alter the default schedule to have Filesystem Clean run more often, please contact Data Domain Support to discuss.
  • Don't schedule Replication to overlap with your active backup window.  Both processes require substantial resources and will complete faster if run separately rather than concurrently.
  • Never use encryption, multiplexing, or pre-compression or client-side deduplication from the client Backup Application (ie. Networker, TSM), as they will greatly reduce the compression factor obtained on the Data Domain system.  Perform these activities on the Data Domain system only. Some backup applications turn on these features by default (ie. HP Data Protector defaults to multiplexing), so please check that all of these are turned OFF for your application.
  • Although the Data Domain system may offer higher limits in configuration options (number of streams, throttling, replication, etc), use of more moderate configurations will often offer the best overall performance.
  • Be certain that you read and understand all alerts from the Data Domain system.  If you don't understand an alert, please call support for clarification.


There are many other configuration recommendations based on what backup application (ie. Avamar, Networker, BackupExec, etc), configuration (ie. VTL, Extended Retention, Replication, Encryption),   and even DDOS version.  See the link below for additional articles that may apply to your particular situation.