Does CIFS client retry?

[Cuong Tran]

Thanks for your response. Yes, the question is, in gist, the server has
responded to WriteX requests with OK status but it does not flush the
changes from its buffers to the disks yet. 

Say, the server then decides that it has "lost" the writes that it has
acknowledged earlier. If the server closes the connection and let the client
reconnects, I think you said that the server cannot rely on the client being
able to retransmit the changes since the server last committed. Right?

My other question is which applications  could break if the server has
violated the commitment and caused the client to reconnect. For lap-top or
work stations, I think Office applications work on temporary files and thus
can retransmit the changes. 

Thanks again.


-- Cuong

> -----Original Message-----
> From: Richard Sharpe [mailto:rsharpe at ns.aus.com]
> Sent: Wednesday, June 26, 2002 11:06 AM
> To: Cuong Tran
> Cc: 'samba-technical at lists.samba.org'
> Subject: Re: Does CIFS client retry?
> 
> 
> On Wed, 26 Jun 2002, Cuong Tran wrote:
> 
> > Hi, I hope the experts could shed some light on my questions here:
> >  
> > Say a CIFS client sends a number of delayed writes to a 
> server. The server
> > acknowledges the writes but it does not commit the writes 
> to persistent
> > storage yet. 
> 
> You mean, when the client sends a WriteX Request, the server 
> responds with 
> a WriteX response with a status of OK?
>   
> > Due to some reason, the server "loses" the writes by the 
> CIFS client. 
> > How does the server recover from this problem?
> 
> You mean that the server has violated its agreement with the client?
>  
> >     (a) Can it ask the client to resend the writes which 
> the server has yet
> > committed to persistent storage? 
> 
> There is nothing in the protocol, AFAIK, that allows the 
> server to say:
> 
>   Oh, by the way, you know that data I told you was safe, 
> well, I screwed
>   up, and you have to send it to me again.
> 
> >     (b) What happens on the CIFS client if the server  
> closes its connection
> > to the client? How much is the application on the CIFS 
> client "shielded"
> > from this type of errors?
> 
> Clients implement reconnect, but it is not clear that all of 
> these issues 
> have been well thought out. If the client still has data that 
> has not been 
> written to the server, it will try to reconnect and flush the data, I 
> believe.
> 
> Regards
> -----
> Richard Sharpe, rsharpe at ns.aus.com, rsharpe at samba.org, 
> sharpe at ethereal.com
>