See “Configuring and using replication” on page 75 for more information about replication.
Deduplication and compression
Compression is applied as part of deduplication. You can expect 1.6:1 compression even on the first
backup where no (or only a small amount of) deduplication can occur. If you disable deduplication,
see “Devices (Configuration)” on page 110, no compression is applied to data on that device.
Tape rotation example with data deduplication
The two most significant factors affecting the deduplication ratio for backup are:
• How long do you retain the data?
• How much data changes between backups?
The following example shows projected savings for a 1 TB file server backup.
Retention policy
• 1 week, daily incrementals (5)
• 6 months, weekly fulls (25)
Data parameters
• Data compression rate = 2:1
• Daily change rate = 1% (10% of data in 10% of files)
Typical savings
The following table illustrates a reduction of approximately 11:1 in data stored. In practice, assuming
1.25 TB is available for backup for this library, this means:
• Without data deduplication: only two weeks of data retention is possible before it is necessary to
archive data offline.
• With data deduplication: even after six months less than 1.25 TB of disk space has been used.
The following table illustrates how this affects the space required to store the data over 25 weeks.
The figures are used to generate the graph shown after the table.
Table 2 Data deduplication savings, example 1
Data stored with deduplicationData stored normally
500 GB500 GB1st daily full backup
5 GB50 GB1st daily incremental backup
5 GB50 GB2nd daily incremental backup
5 GB50 GB3rd daily incremental backup
5 GB50 GB4th daily incremental backup
5 GB50 GB5th daily incremental backup
25 GB500 GB2nd weekly full backup
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