[OpenAFS-devel] Re: safe dropboxing in an anonymous world

[Derrick Brashear]

On Mon, Feb 7, 2011 at 2:26 PM, Andrew Deason <adeason@sinenomine.net> wrote:
> On Mon, 07 Feb 2011 14:04:46 -0500
> Jeffrey Altman <jaltman@secure-endpoints.com> wrote:
>
>> In the dropbox case the client has no need to read anything from the
>> server.
>
> An application writes bytes 0-15 to a dropbox file, then waits 5
> minutes, and continues writing bytes 16-31. In those few minutes, bytes
> 0-15 were flushed to the fileserver because of cache pressure, and later
> were also removed from the cache due to cache eviction pressure.
>
> Now, to write bytes 16-31, the Unix CM needs bytes 0-15, because it
> writes to the fileserver in chunksize-sized chunks. So, it needs to read
> bytes 0-15 again before it can do the write.
>
> That example is obviously completely made up, but I believe this was the
> scenario Derrick was talking about in the gerrit commit message. So, I
> am assuming it is not impossible, though I've never tried to trigger
> anything like that so I'm not really sure at all.

I believe it to be possible but unlikely.



-- 
Derrick