DPM 2010 question


I just got a new job and the company i work for uses DPM2010. The software just runs for quiet some time now, and backups are made to tape. There are 2 servers running DPM and each has a tape library of 23 tapes. 1 tape is the cleaning tape.

Nobody seems to know how the software works and who configured it. Must be some dude that worked here before. Now i decided to jump into DPM2010. Some questions to get started;

1. Everyday DPM generates an error that the free tape treshhold has been reached. We free tapes manually. Is that normal? Can DPM be configured in a way that it automaticaly overrides an older backup?

2. I'm looking in to protection groups. I see there's short-term and long-term protection. What do they mean?

3. Short-term protection is configured to use disk. And it's configured to use tape for long-term protection. Is that the best way to go?

Hope i can get some help! Thanks!
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Thomas RushCommented:
It's common for people to rely less on tape for the daily backups and more on disk.  Disk backups provide a number of advantages to tape, most importantly:
- backup to disk doesn't care if the data comes in slow; if you don't feed tape drives with enough data, you'll cause premature tape media and drive mechanism failures.
- it's typically much quicker to restore from disk than from tape, which might require 24 hours to get a tape from an off-site storage facility, whereas restores from disk can start almost immediately.

That said, you're well-advised to keep tape as a part of your backup strategy, because it provides advantages that disk can't:
- easy off-siting of a second copy for protection of your data in the case of a site-wide disaster
- the best for long-term archive -- it's hard to beat tape for storage of large or huge amounts of data for 5, 10, 20 years or more; tape is designed to hold data for that long with only the most minimal environmental control requirements
- cost -- tape is typically the cheapest storage medium by far when power, acquisition cost, and data center floor space are considered.

For your questions, then:
3) This is common; typically you'll do the daily backup to disk, then copy the backups that you need an off-site or archival copy to tape.
2) "short term" and "long term" aren't hard and fast definitions like "apple"; they are defined by your business needs.  I might guess that data kept for less than a month could be considered "short term", and data which will need to be kept for more than a year is "long term" -- but you need to identify the owners of the data and interview them to understand what their needs and expectations are.
1) Any backup application worth its salt should be able to 'expire' data and re-use or recycle the tapes.  One thing to keep in mind is that you can't expire a backup on a tape and recover that space until the whole tape has been freed up (this comes from tape's inherent streaming access and how tape backup has historically been implemented).  
My bigger concern is that it sounds like you may be keeping all your tapes in the one library... this is dangerous; suppose there's a fire or flood -- all your backups will be damaged or destroyed along with your servers and disk.  You need to have a policy for moving tapes offsite in a formal rotation (look up Grandfather/Father/Son, or GFS, rotation); then you'll be taking tapes out of your library regularly, and replacing them with tapes that are either new, or able to be overwritten.  So you'll need to look at where you keep your data, for how long, and make sure you have a way to get data offsite as well as set some backups as archive class, so that they are saved for legal compliance, possible audit, or certain other inquiries (i.e., the IRS sends you a letter and says, "Let's talk about your 2010 taxes... ").

There's a book (believe it or not!) called "Backup for Dummies" that will help you get started.  Some good free tutorials at www.snia.org also.

One final thought: backup is "easy" -- but backup isn't the business.  Make sure you test your restore processes to know that you know how to get things back should the emergency arise.  It's no good to wait until after a fire or disk crash to find out that your backups won't get you a runnable application, or a server that boots without an immediate blue screen.
SvenIAAuthor Commented:
Thanks for taking the time to post such a comment on my question. I appreciate it!
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