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Multi-member disk media sets and grooming

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Has anyone had success grooming a disk media set consisting of more than one member? If so, how does Retrospect handle the newly-vacated blank space on earlier members of the set?

 

We perform most of our backups to tape. A while back (actually, quite awhile back - it was Retro 8.2), I attempted to implement a Disk to Disk to Tape backup scheme, which failed miserably when the disk backup set became hopelessly corrupted while in a scripted process of transferring its data to tape. I haven't yet had the courage to try D2D2T again, so we only use our disk backups as a convenient supplement to our tapes, to enable quick restores. It was only after adding a second member that I first tried grooming the media set; emphasis on "tried," as something either went wrong during the grooming process that irreparably corrupted the data, or the process encountered damage in the media set that it could not get past. I can't recall if I ever tried to groom under Retro 8.2, but have tried and only failed under Retro 9 and Retro 10. I was at first wondering whether grooming a multi-member media set was a good idea, but I now wonder if it is even possible to do so.

 

Comments?

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Why do you need more than one disk member? What is the size of the media set?

 

(I can't answer your question, since I have never groomed in the Mac version and uses only single member sets in the Windows version.)

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Why do you need more than one disk member?

The answer to that is, we don't under a workable grooming scheme. The multi-member disk set was originally set up in Retro 6 when were periodically recycling the set (and grooming was not an available option), and that scheme was carried forward when we moved to Retro 8.2. We tried grooming as an experiment in lieu of adding a new disk member, without success. So I guess the short answer is, we were using a multi-member disk set because that's what we always had done.

 

I have now set up a new disk media set with grooming and a single member, to see if we can have more success with this arrangement. It would be useful, though, to know whether our unsuccessful experience with grooming multi-member disk sets was unique or might perhaps be exactly what's to be expected.

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I see.

 

At home I have cheap 3TB USB 2 disks. At work we have servers with 4 disks, using RAID-5. And you could get anything in between. A 2-disk NAS for 6TB of storage, for instance.

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I am using this scenario in one case - I have 3 500GB external hard drives connected through daisy chained FW800. (Lacie Quadras if that matters to you) Grooming is working, I'm not sure exactly how it's choosing to manage the free space, but it took much longer than I expected to request the 3rd member. I'm using 10.1.0.221.

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