Replication: Stored Size differences between Primary and Replication sites (DS-Systems)
Summary
This article describes some storage differences you should consider when using Replication.
Details
Only the backed up data is replicated from one DS-System to another. Some of the items that are not replicated are:
- DS-Client database backup files (from v11, these are replicated)
- Logs
- DS-Client configuration settings (e.g. Bandwidth Throttle, DS-Tools, etc.)
Because replication tries to optimize on transmission time and storage, the stored size might differ significantly between the primary (Production) and replication DS-Systems.
- Note: The Protected Size always remains the same for each replicated DS-Client's data.
An invoice generated in DS-Billing for a replication DS-System may show totally different storage numbers than an invoice generated in DS-Billing for the primary DS-System. This might be an issue if you send an invoice for a replication DS-System to your customer. Some reasons for these billing differences are listed below:
Library files
Library files are replicated from a primary DS-System to a replication DS-System as libraries and their information is inserted in the DS-System database of the replication DS-System so that future files with the same content will link to them.
- The invoices in DS-Billing for the primary DS-System are calculated by adding a library amount once for each DS-Client that links to that library.
- Since not all the DS-Clients underneath one account may be replicated from the primary DS-System (you choose to replicate at the DS-Client level), those differences will show up in the invoiced amount.
Master generations
Replication is performed "incremental forever" from the primary DS-System.
- Only the first generation of a file that qualifies for master/delta processing will be replicated as a master generation (including all data blocks).
- Incremental generations will be replicated as delta generations.
- In certain scenarios, the primary DS-System may store more master generations for the same file than the replication DS-System. Those differences will show up in the invoiced amount (stored size).
- All new Windows & Linux DS-System installations will ignore recycled delta generations when calculating 'stored size'.
- This behavior is configurable at DS-System level, by using the Advanced Configuration options "ExcludeRecycleDelta" parameter. For more details, see DS-System Knowledge Base article: "DS-System Advanced Configuration".
See Also
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