Finally, tape-based backup
and recovery regimes are logistically
complex and demand substantial time and care
to administrate. Media has to be managed,
cataloged, and stored in a way that allows
for consistent backup and accurate recovery,
but issues such as personnel changes,
company relocations, the need to accommodate
remote offices, maintaining tape-friendly
temperature and humidity in the storage
facility, and the hassle of validation
testing all invite human error or omission
and inflate IT budgets. In essence, while
tape technology remains a reasonable means
of long-term archiving, it is becoming
continually less viable as a technology for
on-line backup and restoration.
Microsoft Data Protection Manager 2007 radically
changes the reliability and usability aspects of backup and
restore. The key differentiator is that DPM is primarily an
intelligent disk-to-disk based backup solution.
The basic concept is simple. You configure a DPM
server with enough disk storage to hold a complete replica of all
the data you want to protect from all your servers along with
space for the historical changes you want to keep. For a 30-day
history this may require somewhere in the range of 1.5 to two
times the protected data space. The actual disk capacity needed is
highly dependent on how often your data changes. Since disks are
inexpensive and getting more affordable all the time, storage
costs are relatively trivial for most IT organizations.
What is more significant is that a DPM server
can be built with highly fault-tolerant components such as
redundant power supplies and ample redundant cooling. By
configuring RAID 5 or RAID 6 (double parity drives) striping on
the backup disks, reliability is far higher than with tape-based
systems.
Microsoft leveraged key technologies in Windows
2003 to make Data Protection Manager the backup-and-restore
solution of choice. The foundation of DPM is the use of Volume
Shadow Services for creating and maintaining extremely compact
differentials. It does this both on the protected server for
efficiently replicating change differentials over the network to
the DPM server, but also on the DPM server itself for efficiently
storing the historical snapshots used to recover data.
You can gain almost continuous data protection
by replicating data from your protected servers as often as every
15 minutes. This means that if you have a failure on your server,
in the worst case you can restore it to the last 15 minutes. This
is far beyond the practical capability of tape-based backup
systems. Basically, the DPM server always has a complete and
up-to-date replica of all protected data. DPM takes further
advantage of disk technology by storing the data in a Windows
format file system that you can directly navigate to with Windows
Explorer. DPM actually creates separate disk volumes for each
protected server.
Thanks to support for disk-to-disk recovery and
restore, DPM can reduce network recovery time from hours to
minutes and make administrative tasks far more intuitive than with
tape-based solutions.