[tahoe-dev] tahoe backup re-uploads old files

[David-Sarah Hopwood]

On 01/03/12 19:27, Greg Troxel wrote:
> Brian Warner <warner at lothar.com> writes:
> 
>> Yeah, that's a fair argument. I built "tahoe backup" because it seemed
>> the best way to take advantage of tahoe's unique features. The
>> orthogonal way to handle backups, as implemented in a zillion existing
>> programs, generally expects a POSIX-like backend filesystem. Tahoe is
>> both more and less than that:
>>
>> * it has immutable files and directories, which can safely be shared
>>   between subsequent backups
>> * modifying files is expensive, and new files should be written
>>   all-at-once
> 
> True, but I wonder if that means that a tahoe-specific backup program is
> needed, or just one that uses a mostly-posix filesystem in a careful
> way, so that it's reasonably efficient for a class of filesystems.

'tahoe backup' constructs immutable directory trees, which requires each
tree to be built leaves-first. It would be impossible to achieve that
with a POSIX API, which requires that parent directories are constructed
before children.

-- 
David-Sarah Hopwood ⚥

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