Dell PowerVault DP600 - Manual (Page 39)

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Retention Range for Application Data
You can select a retention range between 1 and 448 days for short-term disk-based protection,
up to 12 weeks for short-term tape-based protection, and up to 99 years for long-term tape-based
protection.
For example, if you select to synchronize every 15 minutes and you set a retention range of 10
days, those recovery goals result in a protection plan that maintains 960 recovery points for
application data in that protection group after the initial 10 days of data protection.
See Also
Recovery Goals for Tape-Based Protection
Recovery Goals for Tape-Based Protection
DPM protects data on tape through a combination of full and incremental backups from either the
protected data source (for short-term protection on tape or for long-term protection on tape when
DPM does not protect the data on disk) or from the DPM replica (for long-term protection on tape
when short-term protection is on disk).
The choices for retention range, frequency of backups, and recovery options are different for
short-term and long-term protection.
Note
You can select disk or tape for short-term protection, but not both.
Short-Term Protection on Tape
For short-term data protection on tape, you can select a retention range of 1–12 weeks. DPM
provides management support of your tapes through alerts and reports, and it uses the specified
retention range to establish the expiration date for each tape.
Your options for backup frequency are daily, weekly, or biweekly, depending on the retention
range.
If you select short-term protection on tape using both incremental and full backups, the retention
range will be longer than the one you specified (up to a maximum of 1 week longer) because of a
dependency between full and incremental backups. Tapes containing full backup are recycled
only after all dependent incremental tapes are recycled. Because full backup happen once a
week and the incrementals daily, the weekly full backup tape must wait for the six daily
incremental backup tapes to be recycled before the full backup tape is recycled. If an incremental
backup fails and there is no incremental tape to recycle, the full backup tape will be recycled
earlier.