Corrupted File BU set - File versus Disk for future?

[DaveD]

Environment: Desktop with Win XP Pro SP3, Retrospect Pro 7.7.620, nightly local FILE backup to USB drive, two 1TB BU drives with one off-site, swapped regularly. I recycle the BU sets when the BU disks fill up, approximately once a year. This Retrospect BU strategy has worked well for at least 10 years now, with successful file recovery many times and system recovery twice. I had previously stayed away from DISK backups, but don't remember why (perhaps support of DISK backups in earlier versions wasn't that robust?), and I understand that over the last several years the whole concept and support of DISK backup sets has improved, so now that type of backup is recommended over a FILE backup, even with my 7.7 level. Perhaps I'm sort of stuck in the past and need to rethink this FILE vs. DISK strategy.

 

That concern really came to my attention a few weeks ago when my on-site backup, then several hundered gigabytes in size, became corrupted for unknown reasons. It was not recoverable; I had to recyle it and start over. I just started using a DISK backup for my new laptop, and notice that it consists of many files instead of a single large file with the FILE backup. I suppose that is what makes it groomable? So I am strongly considering going to a DISK backup strategy for my desktop. But I have a few questions that I haven't been able to answer through Retrospect support of this forum.

1. In the instance above, would I have potentially avoided the corruption of my entire backup if it were a DISK backup? Losing one or more of these smaller backup file would have cost me what?

2. In my environment, is one backup type fundamentally more desirable than the other? Advantages/disadvantages of each?

3. The "grooming" concept is a bit difficult for me to understand, not having done it. When I groom, will I still have a complete system backup to restore from, a backup that is simply missing some of the sessions, or nightly backups, in the larger backup? Or will I have to exercise caution when I groom to make sure that I am not ending up with a partial backup, one that would not allow me to do a full system restore to, say, last night's image?

 

Thanks, Dave D

[arachnaut]

I've used File backup long ago, by accident, until I discovered Disk backup. The distinction was confusing to me at first.

 

With Disk backup you choose a folder or drive location for the backup set and CD-sized archive chunks are saved in a file sequence. Each new backup adds to the sequence.

You can recycle the set or groom at any time. Recycling starts a new sequence and erases the old. Or you can specify a new backup set and archive the old sequence.

 

Grooming attributes are configurable - there is a special policy or you can set the number of backups to save (such as the last 10).

 

I do incremental backups each night, with a monthly 'Verify' script followed by a 'Groom' script which is set for 10 backups saved.

 

I rarely have any problems with grooming, but eventually I do see some errors, perhaps due to a nightly power dip or whatever. This may happen a few times a year. The catalog may be recreated from the backup file set.

 

What is odd about the Disk backup is that when you set it up, you specify a Disk drive, not a folder, and Retrospect makes a folder for you. Generally I prefer to specify all this stuff, but that's the way it is.

 

Generally speaking I do an Acronis Image backup periodically for disaster recovery at periodic 'safe' points when I know everything is stable. I do nightly scripted unattended Retrospect incremental backups to recover files or get the system up-to-date from the last Acronis image.

 

I do this because a system restore from Acronis only takes about 15 minutes (I keep the system drive rather sparse.)

[DaveD]

Thanks for the reply, Jim. Your insight and experiences are helpful, but you really didn't answer my questions.

 

I'm sure a member of this community must have the experience that would enable him or her to answer these questions. How about Retrospect support? I believe the differences between and confusion about FILE vs. DISK backups, as is evident by other threads in this forum, is worth a comprehensive answer. This is the type of subject that used to result in the generation of a "white paper" (when that term was in vogue). I'm a bit afraid of moving forward to DISK backups until I feel that my backups are safe and complete, especially when culling parts of them with the groom option.

 

Thanks, DaveD

[Scillonian]

1. In the instance above, would I have potentially avoided the corruption of my entire backup if it were a DISK backup? Losing one or more of these smaller backup file would have cost me what?

2. In my environment, is one backup type fundamentally more desirable than the other? Advantages/disadvantages of each?

3. The "grooming" concept is a bit difficult for me to understand, not having done it. When I groom, will I still have a complete system backup to restore from, a backup that is simply missing some of the sessions, or nightly backups, in the larger backup? Or will I have to exercise caution when I groom to make sure that I am not ending up with a partial backup, one that would not allow me to do a full system restore to, say, last night's image?

 

Item 1: When a .rdb file becomes corrupted within a disk backup set you only loose the files that are contained within that file. Once Retrospect knows which files are lost it will try and back them up again at the next backup if they still exist at the source. I have personal experience of this and the backup set was still usable after one of the .rdb files became corrupted because of a networking issue outside of Retrospect's control. (The network switch crashed.)

 

Item 2: I have no experience with file backup sets - I have always used disk backup sets when writing the backups to local hard disk or local NAS. Personally I think that a disk backup set would be more likely to survive data corruption - whether cause by power failure, network failure or disk defect - than a file backup set.

 

Item 3: Grooming removes any redundant files in the backup set that are not featured in an active snapshot that appears on the snapshots tab in the backup set's properties. The number of active snapshots depends on what grooming policy you set for the backup set. When the grooming policy specifies that an active snapshot is no longer needed it is removed from the list of active snapshots and any files that are only featured in that snapshot are marked as redundant. When the backup set is later groomed - either manually, on a schedule or automatically because the backup set's allocated storage capacity has been reached - these snapshots and redundant files are removed reducing the storage space used. As long as an active snapshot exits for the files that need to be restored then a restore will work.

 

 

John

[DaveD]

John, thanks for your response. You answered my questions, and well. I will now plan to go to disk backups, starting with the next recycle. Then I'll play with it a bit to further satisfy myself that that type of backup is at least as save as a file backup, including after grooming. I may even update to the latest Version 8, although I'm not sure that there is much in the way of enhancements over 7.7 in this area.

 

DaveD

[Scillonian]

John, thanks for your response. You answered my questions, and well. I will now plan to go to disk backups, starting with the next recycle. Then I'll play with it a bit to further satisfy myself that that type of backup is at least as save as a file backup, including after grooming. I may even update to the latest Version 8, although I'm not sure that there is much in the way of enhancements over 7.7 in this area.

 

If you are going to upgrade to Retrospect 8 I would suggest that you do so before starting to use disk backups and grooming. Although Retrospect 8 can write to backup sets created with Retrospect 7.7, there is currently a problem for some (all?) users when it comes to Retrospect 8 grooming backup sets created by Retrospect 7.7. (Please search the forums if want to know more.) This will apparently be fixed in the next version which is currently in testing.

 

As far a backup sets features go, there is no noticeable difference to me between Retrospect 7.7 and Retrospect 8. The new feature in Retrospect 8 Professional that I upgraded for is Proactive Backup which has finally allowed me to fully automate my backups.

 

 

John