Managing Backups With Or Without Media Rotation - HP BB118BV - StorageWorks Data Protector Express Package User's Manual & Technical Reference

Changing the tape set count
You can change either the length of the full data recovery period or the level of access to historical copies
for media rotation plans. By modifying the tape set count, you can lengthen or shorten the period in
which full data recovery is available or the period of time for which historical files are available.
For example, you may wish to increase the number of yearly historical tapes available from two to three
or more. To do so, change the number in the Sets box for Yearly set types on the Schedule property
page to the desired number of historical backups.
Alternatively, you may wish to expand the full data recovery period, while limiting the number of historical
backups. As you change the number of media groups you want to maintain, Data Protector Express
updates the number of sets required for the backup job.
To view when a group will be used during the life of the backup job, select Sample.

Managing Backups with or Without Media Rotation

If you create a backup job that does not include media rotation, you must manage your backup media
sets manually. That is, you are responsible for ensuring that the expected media is in a backup device
before a job runs. Data Protector Express will not prompt you to insert the correct media in a backup
device because there is no media rotation plan to follow.
The schedule types Run now, Run on specific day, Run on selected days, and Not scheduled all require
you to manage your own backup media sets. To make data recovery easier, Data Protector Express sets
the backup mode to Full for any job created with these schedules. Running a job in Full backup mode
ensures that you can use the media set to recover data easily. To change the backup mode for these
jobs, edit the Backup Mode setting on the Options property page.
For all other schedules, you must choose whether or not to include media rotation. You can also alter
the backup mode if the default settings do not suit your data recovery needs. By default, Data Protector
Express sets the Rotation Type to No rotation.
Follow the guidelines below to determine how best to manage your media and how to set the backup
mode.
Determining the length of the full data recovery period
Full reconstruction of data can be accomplished in two ways. The first method requires the most recent
full backup media and all of the incremental backup media since the last full backup tape. The second
method requires the most recent full backup media and the differential job from the previous day.
For example, to reconstruct the data for a Wednesday from a Simple-6 set rotation type, you will require
one of two media sets: either, the full backup media (or media set) from the previous end of week and all
of the incremental media sets from that week (that is, Mondays, Tuesdays and Wednesdays); or, the
full backup media set from the previous end of week and the differential media set from Wednesday.
(In some circumstances, the preceding full backup media set will be a monthly or yearly job and not a
weekly job.) As long as none of these media sets has been overwritten, full data recovery is possible.
The length of the data recovery period is determined by the number of daily incremental or differential
media sets, the number and frequency of full backup jobs (usually weekly jobs), and the media rotation
you selected for the job.
Incremental jobs and full data recovery
Incremental jobs are the shortest and smallest jobs to run, but they present some issues related to full data
recovery. The difference between an incremental and a differential backup is important -- incremental
backup jobs back up only files that have changed since the last full, differential or incremental backup,
while differential backup jobs back up all files changed since the last full backup. If incremental backup
media sets are overwritten or recycled before another full backup is performed, this can create a gap in
available data if you need to recover files from the overwritten media.
Exclusive use of incremental backup jobs to ensure full data recovery after a disaster is not recommended,
unless you are using a schedule that retains one full backup and all subsequent incremental backups
User's Guide and Technical Reference
145