[OpenAFS] Problem for file system navigation in a backup volume tree

[Jeffrey Altman]

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Giovanni Bracco wrote:
> On Thursday 06 December 2007 20:45, Christopher D. Clausen wrote:
>> Jason Edgecombe <jason@rampaginggeek.com> wrote:
>>> Jeffrey Altman wrote:
>>>> And I just added equivalent functionality to the Windows client.  If
>>>> you want to test it, let me know.
>>> Should "-backuptree" be the default? What might that break? I'm
>>> thinking that -backuptree would be the behavior a user expect's when
>>> they use their ~/BACKUP folder in a traditional AFS config.
>> No, it should NOT be the default.  Bad idea.
> why?

Changing this behavior without fully understanding the consequences of
the change is a bad idea.

Doing so would only be a good idea if all of the volumes to which there
are mount points and for which there are .backup volumes used the same
backup policy.

I understand the reason you want this change is so that you can create a
very large storage space that is made up of multiple volumes but which
appears to the user as on cohesive unit.  In such a deployment you want
the set of all volumes that are associated with the same project or user
to provide a consistent .backup image.  That makes a lot of sense.

However, it breaks down when the mountpoints refer to volumes outside
the virtual group perhaps in another cell.  In that case there is no
reason to believe that the .backup of the volume is consistent with the
.backup volume the user is starting from.

Secondly, changing this behavior as part of a minor update would alter
the behavior for all users including many who have not requested and
would not be anticipating the change.  The result would be an unwanted
surprise and that is not a good thing.

The functionality exists and you are more then welcome to distribute
configurations which turn it on for your users.  However, in the four
years that this functionality has been available, this is the first time
that I have heard anyone request it on the list.  Therefore, I am sure
that it has not received significant use.  We can reconsider changes in
the default settings for the next major release series.

Jeffrey Altman

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