[Box Backup] I have the fear....

Chris Wilson boxbackup@fluffy.co.uk
Tue, 13 Mar 2007 22:40:39 +0000 (GMT)

Hi Ben,

On Tue, 13 Mar 2007, Ben Summers wrote:

> If we included hashes of file contents, it'd sort it.


> But then you'd 
> have to calculate hashes for everything when you scan.

Doesn't seem like a massive overhead, especially if we cache the hashes of 
large files (over threshold) and we can recalculate the hashes of small 
files on the fly.

> We don't check file sizes though. That would make it less likely to miss 
> things, at the cost of included them encrypted in the directories.

That would be a nice feature, but wouldn't catch every case. For example, 
in the test case I just wrote, both files deliberately have the same size.

> So really there's no real way of catching this case without a massive 
> amount of book keeping and inflating the structures.

I don't agree, I think that encrypted file sizes would be easy and result 
in a minimal overhead, and partially-cached file hashes would probably be 
ok too, especially as users can set the threshold for caching them.

> How about
> 4. Wait until the next version when we intend to use filesystem change 
> notifications instead of scanning, where available.

I agree with you and Martin that this is worthwhile, however I think it's 
worth adding support for the other options given that not all platforms 
support change notifications (does BSD or MacOS X?)

> For now, document this edge case.

Yes, definitely.

> Changing anything now seems an awful lot of extra work to work around 
> non-optimal (or dangerous?) behaviour in an obscure Linux distribution 
> with dubious project goals.

Sorry, I don't agree with this, I happen to like Gentoo a lot and have a 
lot of respect for them, especially the technical support which seems to 
be lightyears ahead of mainstream Linux distributions like Ubuntu.

Cheers, Chris.
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