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

[Andrew Deason]

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.

-- 
Andrew Deason
adeason@sinenomine.net