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Smart remove - still do not understand it

Asked by Guenther Erhard

Hi Dan,

I've read the discussions and I'm afraid I still do not understand the smart remove feature.

You say that unchanged files are represented by hardlinks and changed or new files by copying. Where does BIT copy these files? If they were in the folder of the removed snapshot they will also be deleted.

For example:
I have done an initial snapshot on Sunday and then had daily snapshots of a folder for one week.
On Tuesday file1 has changed - so I assume that the original file1 is in the initial snapshot folder and the altered one is in the Tuesday snapshot folder. The Monday snapshot would contain a hardlink to the file in the Initial folder and the others contain hardlinks to the file1 in the Tuesday folder.

Now I remove all snapshots except the initial and let say the saturday snapshot. From my undestanding the Tuesday folder will be removed and therefore also the modified file1. The hardlink in the Saturday snapshot would direct to an empty position. This means I could not restore the modifed file1 in case I have deleted it today. Only the version contained in the initial snapshot would be available.

Did I get this wrong?

Thanks,
Guenther

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Dan (danleweb) said : 		#1

Hi,

Hard-links works on only on files.
For more information about them: http://en.wikipedia.org/wiki/Hard_link

Hard-link is a feature of file-systems. FAT don't support them so snapshots will copy all the files.

The basic idea is that file name is stored in one place and the data in another with are reference counter. When you create a hard-link there will be a new name that will point to the same data and will increase the reference counter. When you remove a file the system will remove the name and will decrease the reference counter. If there are no other references it will remove the data too.

Regards,
Dan

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thndsr (stijnverwaaijen) said : 		#2

Hi Dan,

I don't think you answered Guenther's question (but I could be wrong). Let me put it more simple: when the first snapshot is deleted on 'smart remove' won't the initial data be deleted so the hard links point to empty spots?

Best regards,

Stijn

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