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Qrecall file format?  XML
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Chris Caouette



Joined: 30-Aug-08 19:43
Messages: 39
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I am always nervous about a backup to an unknown file format. Is there a way to recover if the backup file gets an error? What happens if Dawn to Dusk stops production on Qrecall? I had this happen already with a nice backup program that was going great then suddenly the company shut down.

I am not having a ton of luck with Time Machine (I have 3 computers and the drive is a 1TB on a AEBS). Qrecall looks like the answer but I am just making sure I have my rear covered.
Thanks!
Chris

Lots of Macs here!
James Bucanek



Joined: 14-Feb-07 10:05
Messages: 1548
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Chris Caouette wrote:I am always nervous about a backup to an unknown file format.
I sympathize with your concern.

QRecall archives use a proprietary file format. There is no commercial filesystem available that provides the kind of storage organization that QRecall needs. So it simply isn't possible to provide the kind of features that QRecall does with an existing filesystem. (In an interesting footnote, Apple couldn't implement Time Machine with the standard HFS+ filesystem either. Apple had to alter the HFS+ volume format to get Time Machine to work.)

Is there a way to recover if the backup file gets an error?
Absolutely. QRecall includes a comprehensive Repair command that will systematically scan the raw data blocks of an archive, clear out any damaged data blocks, and reassemble all valid data back into a functional archive.

QRecall archives, unlike standard filesystems, were specifically designed with data recovery in mind. Filesystems are designed to be fast. QRecall archives are designed to be robust and compact. The archive contains several levels of redundant information so that the loss of archive data limits the loss of information to the fewest number of captured items as possible.

In fact, I would go so far as to encourage anyone who's interested to put this to the test. Create a QRecall archive, then use a Hex editor or some other method to poke holes in the archive data, run a Repair, and see what happens.

Archives also contain internal consistency checks that standard filesystems don't have. Every block of data in an archive includes a checksum, which is verified every time that data is read. There have been more then one QRecall user who discovered a drive that was occasionally returning invalid data because QRecall, and QRecall alone, complained when reading from that volume.

What happens if Dawn to Dusk stops production on Qrecall?
I will be very sad. The QRecall application, however, will continue to run. If the future of the application puts your data at risk, you can always recall it to a traditional filesystem and re-archive it using other means.

I had this happen already with a nice backup program that was going great then suddenly the company shut down.
I feel your pain.

I am not having a ton of luck with Time Machine (I have 3 computers and the drive is a 1TB on a AEBS). Qrecall looks like the answer but I am just making sure I have my rear covered.
You're welcome to try QRecall free of charge to see if it meets your needs. If you have questions, problems, concerns, or suggestions, the forums are always open.

This message was edited 1 time. Last update was at 31-Aug-08 09:38


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Chris Caouette



Joined: 30-Aug-08 19:43
Messages: 39
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Thank you for the comprehensive reply! I think I will give it a go. I have Time Machine one more go and I still am not having great success. I'll Setup Qrecall and see how it goes.
Thanks!
Chris

This message was edited 1 time. Last update was at 31-Aug-08 09:37


Lots of Macs here!
Clemens Oertel



Joined: 12-May-07 04:13
Messages: 2
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Hi,

The authors of another backup tool provide a detailed technical description of their backup format, as well as the source code for a restore-only command line utility. While I am not using this tool for different reasons, I find this approach very reassuring.

It has happened to many various times that software stopped working from one day to the next, "unexpectedly quitting" on every start, without any obvious reason. Software might not be compatible with future Mac OS changes. In the last year, various small software companies have been bought only to have their products discontinued by the new owners.

I am not suggesting that any of these scenarios will befall QRecall, but one simply never knows. Being able to access data under all circumstances is especially important for backup software, I think.

Any comments/thoughts would be appreciated.

Thank you,
Clemens

This message was edited 1 time. Last update was at 26-Apr-13 06:11

James Bucanek



Joined: 14-Feb-07 10:05
Messages: 1548
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Clemens Oertel wrote:The authors of another backup tool provide a detailed technical description of their backup format, as well as the source code for a restore-only command line utility. While I am not using this tool for different reasons, I find this approach very reassuring.

I'm not philosophically opposed to documenting QRecall's file structure, or even providing code that can read it. The only reason I haven't do so is due to resources and practicality. The QRecall file structure is not trivial. I could probably document it with a few days work, but that really wouldn't help anyone; you'd have to spend another month writing code that could decode it. I could provide much of that code, but again—even if you were a programmer—you'd still have a boatload of work to do to get any useful information out of an archive.

Two, more practical, solutions are already in the works: a command-line version of QRecall and a filesystem driver that will mount a QRecall archive as a volume. I think either of those solutions would give you the kind of "back up" recovery method you're looking for.

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Clemens Oertel



Joined: 12-May-07 04:13
Messages: 2
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James,

Thank you for your reply, much appreciate it.

I agree with you, having alternative access methods goes a long way. Esp. the file system access sounds very promising. If you could consider making the code for that driver available eventually, and throw in some documentation, I'd consider the case closed

But I do understand that resources can be an issue, it is more a piece of mind kind of thing, nothing urgent.

Thank you,
Clemens
Adrian Chapman



Joined: 16-Aug-10 10:30
Messages: 72
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Chris Caouette wrote:Thank you for the comprehensive reply! I think I will give it a go. I have Time Machine one more go and I still am not having great success. I'll Setup Qrecall and see how it goes.
Thanks!
Chris

Chris

I abandoned Time Machine years ago due to its unreliability and total inability to put things right when they went wrong - which was often. I have been using QRecall ever since and while there are occasional hiccups they are rarely, if ever due to QRecall itself. The application is very robust and does a damned good job of looking after my data. I use a Drobo FS NAS for my archives which is not exactly a speed demon but it works well enough with QRecall.

Oh, and one more thing, you won't get better technical support anywhere else. James usually responds within hours to any request for help and he won't abandon you either.
 
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