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Backup strategy design/implementation

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I'm running Retrospect 7.0 on Windows 2000 Advanced Server. It's backing up a group of Windows servers and a group of Mac servers.


The tape drive/changer is an 8-tape magazine DLT IV (40 GB/80 GB). A full backup of the Windows machines fits on 1 tape, a full backup of the Mac machines fits on 2 tapes.


What I'd like to do is have 4 backup sets for each group, each covering 1 week. Each group gets backed up on alternate days (Sat/Mon/Wed and Sun/Tue/Thur) with the "incremental" backups being done to seperate tapes (so it's one Normal backup, then two Normal New Member backups). This requires 7 tapes (3 for the Windows side, 4 for the Mac side because the first backup spans 2 tapes).


I want to minimize tape changing, so I'd like to re-use the 4 "incremental" tapes every week, while saving the "full" tapes for a month each. This would mean changing 3 tapes 1 time per week.


What I can't figure out is how to automate the erasing of the "incremental" tapes every week.


For example, after the first week I have the following in the changer:


1-Windows Week 1

2 Windows Week 1 ("incremental" 1)

3-Windows Week 1 ("incremental" 2)

1-Mac Week 1

2-Mac Week 1

3-Mac Week 1 ("incremental" 1)

4-Mac Week 1 ("incremental" 2)


During the week, I'd remove 1-Windows Week 1 and 1- & 2-Mac Week 1 and replace them with blanks/erased tapes to be ready for the coming weekend's "full" backups.


Then, on Monday I'd like to automatically erase 2- & 3-Windows Week 1 and 3- & 4-Mac Week 1 so that they can be re-tasked as 2- & 3-Windows Week 2 and 3- & 4-Mac Week 2.


Is there a way to do this, or does the tape erasing have to be done manually?

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Pretty much any time you have to manually erase tapes it means that you are doing something that Retrospect wasn't designed for. You can't reuse the full backup like this.


In my experince, complex tape rotations tend do get fouled up even if they do minimize the number of tape changes. That means the backups don't run so naturally restores fail. I also think that storing each incremental on a seperate tape is probably overkill.


How about this:

Plan on using 4 sets of 6 tapes (one set per week)

Use a total of 8 backup sets (one per group per week)

Perform the first full backup, the next day do one "new-member" and then do "normal" backups after that.

Change all the tapes every time you open the loader


Another thing to think about would be storing a full backup on a hard disk for easy restores. Then you could dedicate the tape for longer term archiving.




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There are a lot of factors that are inflexible, unfortunately.


I was contracted to re-build this backup scheme, subject to the approval of people who might not be totally rational about backups.


It was hard enough to convince them that 1 full and 2 incremental tapes was "safe", it might be possible to talk them down to two tapes per group, but it also might not be worth the hassle.


Large scale tape changing isn't really an option. The person who will be doing the tape changing is on a different floor than the tape changer, and also wants the changing kept to a minimum so others can easily cover for her if she's out (illness/vacation...). They'd rather not have to teach a non-technical backup how to remove the magazine and empty/reload it manually.


They also want to store 1 full backup off-site for a certain number of months (I think they settled on 6). They also don't want to spend too much money, so we're limited in the number of tapes available in total (I think we have 26 total, including the ones that will be taken out of circulation each month).


There is no available disk space to store a backup.


When you say "You can't reuse the full backup like this." does that mean if I manually erase the "incremental" tapes that I'll be unable to get files off the associated weekly (which was the first normal/full backup of the set)?


I understand that if someone wants File X from Week 1 (and we're in Week 3), that they're stuck with either the version from the first (full) backup from Week 1 or the one from Week 2 (if it still exists) and any changes that might have been caught by the "incremental" backups during Week 1 are gone.


If someone modifies a file in the time between the first Normal backup and the 2nd New Member Normal (incremental) backup, does Retrospect note in the catalog that the only copy of the file is on the 2nd tape (even though it's still physically on the 1st tape)?

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dan, do your self a favour go check out BRU.


i an in exactly the same position as yourself, after spending a wad of money on retrospect, I find it is not that "professional" after all, that is compared againt "real" industrial strengh software


you cannot erase the tapes ,other than by hand, which means after a year you can have several hundred partially useful tapes.

also you cannot "blank" a tape, only erase it, which means you must continually monitor the server for the next tape to use.

and if you want to re-use a tape , you actually HAVE TO KNOW its future name, because you HAVE to name it.

I suspect your users are the same as mine, they need a simple "flag" telling them to change the current tape, and insert a new one.


I.E an email, but even this simple functionality is not available, you have to go to the server login as ROOT!!!!

start retrospect, check the script , see if the current media is useful, and in to change /format


Yep right like i am going to give a tape changing staff root privs!!.



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"... wants the changing kept to a minimum so others can easily cover for her if she's out (illness/vacation...). They'd rather not have to teach a non-technical backup how to remove the magazine and empty/reload it manually."


This actually is why I proposed changing all the tapes.


With the plan you described in your first post the users will need to be able to dsitinguish between a tape containing incrementals and a tape containing the full backups. This can only be done by manually launching Retrospect and viewing the loader contents. People who don't know backup or Retrospect have a _really_ hard time with this. It makes backups much more likely to fail.


The user needs to understand that the backup criteria they have specified will require some modification or more tapes. 26 tapes simply isn't enough to perform regular backups and keep 1 set per month off site for 6 months.


4 X 3 Tapes for Weekly Windows sets

4 x 2 Tapes for Weekly Mac sets

6 x 5 Tapes for Monthly off site rotation and storage for 6 months


That is 50 tapes by my reckoning


In regard to erasing the incremental backups and reusing the full:

It is "possible" but _definitely_ not practical. It requires a lot of manual intervention every time the incrementals are removed and overwritten. You would need to open the backup set properties, set the two tapes as missing and then manually erase the tapes.


Another way would be to rebuild the catalog file using just the first tape however you will need to set up all your scripts again. It just isn't practical...


It isn't free but I'd suggest something like this:

Can you get extra magazines for the loader? That way the user could just swap magazines instead of messing with individual tapes. You could have 4 weekly magazines that always have the right tapes in them. Another empty magazine could be loaded with off site backup tapes as needed.


Hope that helps


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One more thing that may help claify this:


Retrospect uses Progressive Backup instead of standard full/incremental backup.

As a result Retrospect does not differentiate between full and incremental backups. It is designed so that the user doesn't have to know about them either. It makes restores much easier.


In _every_ backup Retrospect compares the contents of the backup set to what is on disk. Anything that is on disk but not in the backup set gets copied. This is true for the first backup or any subsequent backups.


Thats why reusing the incrementals is so difficult.



Nate @ EMC Dantz Support

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