Move chunks into existing storage

Christoph     Feb 10 2:50PM 2018

While I was testing duplicacy, I backed up only part of what is now my repository (and for which I created a new folder in the backend storage. It occurs to me that I could probably move all the chunks from the test-folder to the now active storage to safe some upload time. Both storages were initialized with -chunk-size 1M -e

Are there any pitfalls to watchout for when I do this?


gchen    Feb 10 8:36PM 2018

I'm afraid that won't work. For an encrypted storage, encryption keys are generated randomly so unless you used the -copy option to copy the config file, chunks are incompatible between these two storages.


Christoph    Feb 11 2:40PM 2018

Okay, at least I now understand the copy option...


towerbr    Feb 17 4:33PM 2018

I did a backup to a local storage and now I'm trying to copy it to a remote storage. I did an init in the first and an add in the second, both with the same chunks parameters, encrypted, but with different passwords.

When I try to copy I get the message:

ERROR CONFIG_INCOMPATIABLE Two storages are not compatiable for the copy operation

The passwords have to be the same?


gchen    Feb 17 10:23PM 2018

When you add the storage using the add command, you'll need to specify the -copy option, otherwise the two storages won't be compatible with each other (i.e., they will have different seeds for the chunk splitters such that the same files will be split into different sets of chunks).


towerbr    Feb 18 7:31AM 2018

Sure, my mistake, RTFM ...

One more parameter to my script ...

Thanks!


towerbr    Feb 18 7:41AM 2018

An additional question: if I use the -bit-identical option, and use Rclone to synchronize local storage with the cloud storage, can I make backups for any of the two, and when they sync will everything be ok? (of course, since I always sync with Rclone after a set of backups).

Ex: I make some backups to the local storage, then I run Rclone, and the remote storage is updated. Then I make some backups to the remote storage, run Rclone, and the local storage is updated.

In this case, since I'll not select specific snapshots, revisions, etc, have any advantages or disadvantages in using duplicacy copy instead of rclone sync?


Christoph    Feb 18 7:51AM 2018

BTW, why is -copy not the default for the add command? Seems like that would make sense.


towerbr    Feb 18 8:08AM 2018

Another doubt (sorry, I'm evaluating the possibilities): if I make 3 backups (revisions) to the local storage and set up a script to always copy the last backup to the cloud storage (it would copy only revision "3").

If all goes well, fine. But if the copy is interrupted, the revision "3" will be "broken" in the cloud storage.

If I make a new backup to the local storage ("4"), and then make the "last" copy, the "4" will be copied to the remote storage.

Any problem with that? Will the prune command delete the partial "3" in the cloud storage in the future?

Maybe I can also use a tag in backup ...


towerbr    Feb 18 8:09AM 2018

BTW, why is -copy not the default for the add command? Seems like that would make sense.

I think it's because you might want to specify one or more additional storages with different patterns of chunks, etc.


Christoph    Feb 18 5:56PM 2018

BTW, why is -copy not the default for the add command? Seems like that would make sense. I think it's because you might want to specify one or more additional storages with different patterns of chunks, etc.

Well, that would work just fine with -copy as default. As soon as you specify a chunk parameter, that will obviously overwrite the -copy option.


gchen    Feb 18 11:24PM 2018

if I use the -bit-identical option, and use Rclone to synchronize local storage with the cloud storage, can I make backups for any of the two, and when they sync will everything be ok? (of course, since I always sync with Rclone after a set of backups).

Yes, when the -bit-identical option is used, the two storage directories will become identical and rclone sync should work as expected.

But if the copy is interrupted, the revision "3" will be "broken" in the cloud storage.

If I make a new backup to the local storage ("4"), and then make the "last" copy, the "4" will be copied to the remote storage.

Any problem with that? Will the prune command delete the partial "3" in the cloud storage in the future?

If the copy command is interrupted, the snapshot file for the revision "3" will not be copied so you'll just end up with some unreferenced chunks in the cloud storage.

why is -copy not the default for the add command?

The -copy option takes a storage to copy the config file from, so it can't be a default option.


Christoph    Feb 19 10:30AM 2018

The -copy option takes a storage to copy the config file from, so it can't be a default option.

I thought about that too, but thought it would be obvious that the default option would be -copy default...


gchen    Feb 19 12:03PM 2018

I think the user should be made aware if the new storage is copy-compatible with the default one. Sometimes you may want to back up to multiple storages directly instead of using the copy command.


Christoph    Feb 19 3:05PM 2018

I'm not sure I understand the argument. Let's assume a user adds a storage to an existing repository and is not aware that the new storage is copy compatible with the default storage. So what? That user obviously won't do a duplicacy copy ... but what's the problem with that? They can just backup to multiple storages as they can now. Or am I missing something?


towerbr    Feb 19 7:12PM 2018

so you'll just end up with some unreferenced chunks in the cloud storage.

And these chunks will only be removed if I run the prune command with the -exhaustive option, right?


gchen    Feb 19 11:28PM 2018

And these chunks will only be removed if I run the prune command with the -exhaustive option, right?

Right, this is correct.


Christoph    Feb 20 3:43AM 2018

@gchen, did you see my post above?


gchen    Feb 20 2:23PM 2018

When you make the new storage copy-compatible with an old one, you copy not just the chunk size parameters but also others like the chunk seed and the hash key, which may leak to some security risks if you choose to encrypt the storage.

Even without this argument I would still think it is not a good idea to make the copy option a default one, as it shouldn't be doing too much for the users. Sure, the incompatible error message is annoying, but at least you'll be greeted by this error message early and it is not hard to fix. On the other hand, if you copy from the default storage by default without noticing it, then there might be corner cases where you'll caught by surprise much later and it won't be easy to change the config.


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