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Do I need multiple media sets?

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From the docs:

 

Retrospect uses an archival method of backup that ensures backed up files are not deleted or written over until you request it. That way, they stay on the backup media indefinitely. For example, if you have been working on a particular document over a period of time, Retrospect backs up a different version of the document each time you back up. If necessary, Retrospect lets you retrieve a previous version of the file from any point in time it was backed up.

 

We are using NAS as the backup device, and the NAS is sync'd to a second NAS on another physical site.

We also do a monthly full backup archive to tape.

 

As the NAS is synced off site we should only need one media set?

 

Adding media sets increases the disk space used.

 

Is there any need/point/advantage in having more than one media set (e.g. multiple daily or weekly media) for the backup?

 

Thanks

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You should only need one media set on the NAS unless you want break your clients into different groups.  In my case because I can not get all my clients overnight I separated my clients into multiple groups and used different media sets for each group all on the same NAS.  You will still need a tape media set for your monthly full backup to tape.  If you are using only one disk media set and it becomes corrupt and unrecoverable then you will lose everything and have to start over from scratch.

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According to Retrospect tech support (during our conversations with them over the last several years) you definitely may need multiple media sets.  Though there is nothing to be found in the (aging) Retrospect user manuals about backup set size limitations, tech support has indicated rough guidelines to us as follows:

  1. Be aware that the bigger you allow your backup sets to become then the bigger your headache should you find you want to do, for instance, some of the following:
    1. rebuild catalogs -- the bigger the catalog is the longer it'll take to rebuild -- this can mean several addition hours *or days* for a rebuild to complete.
    2. manually deleting snapshots from a backup set may take significantly longer, the bigger the backup set (and associated catalog)
    3. Although tech support has told us a backup set can get to the vicinity of 12 million files before it starts to run into problems they have actually recommended keeping the count below 7 or 8 million.  We, accordingly, aim to keep the count below 3 or 4 million, thus we have several more backups sets than we otherwise would want.
      1. By the same token we limit the size, in gigabytes, of our backup sets.
    4. Should you want to move some but not all your backup data to a different physical disk you have a bigger job in front of you if your backup sets are not broken into smaller, more manageable sizes.
    5. I suspect catalog files are more susceptible to corruption the bigger they are.

We would love to be able to backup our data to larger, fewer backup sets; Retrospect management becomes much more complicated if you're having to have more backup sets than what your needs dictate; but experience, certain limitations of Retrospect, and informal recommendations from tech support have taught us that fewer, bigger backup sets is the path to madness.

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You should only need one media set on the NAS unless you want break your clients into different groups...

 

According to Retrospect tech support (during our conversations with them over the last several years) you definitely may need multiple media sets.  Though there is nothing to be found in the (aging) Retrospect user manuals about backup set size limitations, tech support has indicated rough guidelines to us as follows:...

 

Thanks for the help.

 

I don't mind having multiple backup sets for different servers and usergroups.  The main thing is to know if it's enough to rely on just one media set for each Server/group.  We are below the 3 million file count.  So looks good  B)

 

If you are using only one disk media set and it becomes corrupt and unrecoverable then you will lose everything and have to start over from scratch.

 

Do Retrospect disk backups become corrupted often?

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[snip]

 

 

Do Retrospect disk backups become corrupted often?

I agree w/Lennart's response but with a clarification:  In my experience the data in the backup set doesn't often become corrupted, and if it does it's a relatively small portion that does.  The catalog file that indexes that data, however, becomes corrupt more often.  Mercifully, that has become less of a problem than in earlier versions of Retrospect, but we have had to rebuild one or two catalog files this year.  Tech support can never explain why these corruptions occur; they just tell us to run the catalog rebuild tool.  My experience suggests that if the backup set is on some other server than the Retrospect server then corrupt catalog files become much more likely.  Proceed with much caution when considering that scenario, even though the user manual makes it sound like putting backup sets across the network is a completely acceptable thing to do.  Maybe the latest versions of Retrospect are more robust in that regard, I'm just not willing to go to the pain of finding out.

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Just to clarify when I said media set getting corrupted I was talking about the catalog file however if you do not use version 10.5 you might run into issues where you will not be able to even rebuild the catalog file and have to recycle the media set.  The other advantage of having multiple media sets is that when you have to rebuild the catalog it will take less time as there is not as much data to index.

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