Changing the time on a DS-Client

This article describes the importance of setting and maintaining the correct time on the DS-Client and  the source computers the DS-client is protecting.

Consequences of changing the computer time on a source computer

• "Last modified time" of a file may cause problems. If you modify a file after changing the time, its time may be earlier than a version of that file that was already backed up.

• Otherwise, the impact from a backup perspective is minimal.

Consequences of changing the computer time on a DS-Client

1. Reports may show inconsistent data
2. Backup session may show inconsistent data since everything within reporting and generations are based on time.

However, the problems for the DS-Client can run much deeper because the current time on the DS-Client computer is automatically used during some processes:

• Any restore where you select "latest generation of data" may restore an old backup (e.g. if you change the time back before the time of the actual backup session with the latest generation).
• Retention may not have the required effect because it will count backwards from the changed time on the DS-Client (e.g. if your retention rules are based on keeping data for a number of days like "Keep all generations for the last 30 day(s)").
• These are only a few potential problems. There are a lot of variable scenarios that will be unique to each customer’s environment.

If you must change the time on a DS-Client, it may be better to stop backing up all the defined sets (suspend them), clone them and continue with new backups using the cloned sets. This is probably not something that customers will want, however it is the only way you can ensure that future operations have the required effect.

NOTE: These problems are most likely to occur if the time on the DS-Client computer is changed backwards. Problems will occur if the next backup session runs at a time that is before the time of the most recent backup session.