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Backing up OS X 10.4 while OS is running?

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I have two questions related to "open files" during a backup:


1) In the XP version, Retrospect uses a function of XP to sucessfully back up files that are in-use during the backup. This is goodness, since the backup process can run while the OS is running, and the backup will be valid and up-to-date when it finishes.


How does Retrospect for Mac deal with this issue under OS-X v10.4?


2) Also, a related question to a very special case of backup: If backing up the boot volume to a file backup ON THE SAME VOLUME, what is the state of the finished backup set? (I know, an odd way to do things but there is a special case.)

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(1) It can't back up open files because it can't open them. Any backup program would have this issue.

See this thread for a discussion of the issues:

Is a Duplicate an exact duplicate?

Even if Retrospect were to be able to get a copy of all open files at an instant, it still wouldn't be good for a restore of databases. See the above thread for a discussion. You really need to back up a quiet system.

Even the Windows recommendation is, for things like database servers, get the database program to save its own self-consistent backup copy, then back up that backup copy.


Note that the recommended way to do a bare metal restore is to restore the OS first, then restore on top of that, which will get you what you want.


(2) obviously, the file won't get backed up. Same thing for catalogs. You would need to do a catalog rebuild on your last catalog that got saved out (or else, as is recommended, back up your catalogs separately).



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Thanksk for your insight.


I have no conceptual argument with what you describe, but I wonder, given thise (quite valid) issues you describe, how you see a function of the Windows Retrospect that claims to do just that -- deliveer an online backup tthat allows for a valid bare-metal restore.


Specificaully, Retrospect calls it "Open File Backup", which uses a Windows XP system service called "Microsoft Shadow Copy". My understanding is that as the backup begins, this service seems to briefly freezes the fiile system to accomplish this) and takes a snapshot of all open files (I['m assuming a checksum, actually) as well as any files that are opened duinrg the backup. At the end of the backup, Retrospect (in conjunction with Microsoft Shadow Copy) appends to the Retrosect backup any changed that have to be made during the backup. Then, on Restore, it combines any such late changes with the oriinal files on the backup, yielding a valid Restore.


Do you feel that this process is indeed successful at what it is doing? If so, why couldn't the Mac OS incorporate similar functionality?



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why couldn't the Mac OS incorporate similar functionality?


Because that's not how unix works. See the link in my post above regarding a RAID 1 mirror split, which is the only way of which I am aware to "freeze" a filesystem at an instant (and which is still not sufficient to back up a database in a consistent state - see the link in my post above for a discussion).



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