On 8/29/10 10:16 AM, martin f krafft wrote:
>
> What I think BackupPC is doing right now is:
>
> 1. It starts receiving a file
>
> 2. After a certain time, it has enough information to take a guess
>     at the corresponding pool file, and opens it.
>
> 3. What seems to happen now is weird: the FileIO method fileDeltaRxNext is
>     called repeatedly, but at the same time, the client keeps sending data, 
> not
>     checksums.

I haven't followed the code, but I think the idea is that if the file - or 
maybe 
the difference from the existing guessed match - fits in memory it doesn't need 
to write a tmp file before writing to the pool.  I'm not sure if the rsync 
protocol allows switching from 'no file' on the receiving side to having 
checksums to match in mid-file even if the initial filename is correct and not 
a 
hash collision.

> Here's what I think should happen instead:
>
> As soon as at least one candidate file in the pool is found:
>
> 1. Keep the received data (2×128k) in memory;
>
> 2. Somehow convince the peer that we actually have the file and that
>     it should continue sending block checksums, or however the rsync
>     protocol actually works;

Not sure this is possible, and even if it is you still have to deal with hash 
collisions detected later.

> Does this make sense?

Only on bandwidth-restricted connections.  On a LAN you can usually transfer as 
fast as the remote can read the file anyway.

-- 
   Les Mikesell
    lesmikesell AT gmail DOT com



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