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Moved files - can use the same Backup Set?


cfieldgate

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Hi,

 

I have moved a large number of files (two sets of ~3TB) from one NAS to a new one using rsync. This avoided tying up my backup server (which runs Retrospect backups nightly) and allowed normal (client and NAS) backups to continue. It took several days to complete the rsync jobs!

 

To continue running backups on the new NAS, can I simply change the source in the backup script to point to the copied files on the new NAS, and if so, will it back them all up again, thinking they are new files? I don't really have the storage space to create a new backup and I don't want to lose the current backup until I know all is working correctly.

 

Any advice would be most welcome.

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In theory if the copied files are exactly the same as the original files then they should not get copied again and Retrospect will just note their new location in the snapshot. Practice though is a different matter. When I have moved files between volumes in the past I have found that some files are seen as changed and get backed-up again.

 

When you ran rsync did you ensure that the timestamps (and other metadata) from the original files was preserved? It only needs one of the timestamps (or other metadata) to be different for Retrospect to see the file as changed and back it up again.

 

Do have enough spare storage space to run a test backup of a subset of the files? Create a new backup set and script and backup some files from the old location to it then change the script source to the new location and run a backup again. This should give you an idea of how many files Retrospect is going to see as changed.

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Scillonian,

 

Many thanks for the very quick reply :) .

 

I guess another way to test would be to transfer a subset of the files from the current backup set to a new backup set and then try a backup of the files at the new location to the new backup set - that may be quicker as there would be no network overheard in the backup set transfer. I should be able to make enough backup space available to run a representative test - I just don't have ~6TB+ spare right now until the old NAS is re purposed (as backup storage).

 

As for rsync, as far as I know the timestamps etc. transferred identically - Linux to Linux. There were no errors or other messages in the logs, so I may be "lucky". :D

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Yes. EXT4. Different makes though (Synology and QNAP)

Synology and QNAP appear have different implementations of Ext4 at present. From what I can figure out QNAP are using 32-bit superblocks (which is one of the reasons why QNAP volumes can't be expanded beyond 16TB) and Synology is using 64-bit superblocks.

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A tip you may find useful:  When you wish to see how Retrospect is going to handle files that you think are matching files I think you can create an "Immediate Backup" (under Backup on the left columnar menu bar).  It has a "preview" function whose results will tell you which files/folders it is going to backup and which ones don't need to be backed up because they are already in the backup set.  Play with that a bit and see if you agree.

 

As you test don't be surprised if your results are confusing -- in past tests I've done it really wasn't always clear what logic Retrospect is using to determine if two files -- that you are certain *do* match -- were considered a match by Retrospect.

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