Re: Log file for CM

[Luis Bernardo <bernardo@math.lbl.gov>]

On Fri, 18 Sep 1998, David M. Malon wrote:

> >
> >  Luis Bernardo wrote:
> >  >
> >  > I evaluated the total transfer rate as a function of the time during the 6
> >  > hours the tests ran (around 23000 seconds). The total transfer rate is the
> >  > sum of the individual transfer rates at any given time (approximately).
> >  > A plot of the transfer rate is include in the .pdf file I attach. As one
> >  > can see when things go "well" we get a transfer rate around 3 MB/sec but
> >  > most of the time things don't go well...
> >  >
> >  > Luis
> >
> >  Arie wrote:  It looks more like 6 MB/sec at the peak.
> > 
> 
>    The highs (and some nonzero lows) may be artifacts of the rate-summing
>    method.  I am not sure of the method that Luis is using.

I only have the time a stage was requested, the time it was completed and
the file size.

> 
>    Suppose Joe and Bob each issue a request for a different 10-MB file at
>    time 0.  Suppose HPSS immediately services Joe's request, and delivers his 
>    file in 10 seconds, while Bob's request simply waits.  Next, Bob's file is
>    delivered during the following 10 seconds.  The system delivers data at the
>    constant rate of 1 MB/second for 20 seconds, but the rate summing method
>    makes things look different.  Because Joe's request was issued at time 0 and
>    completed at time 10, Joe sees a rate of 10 MB/10 seconds = 1 MB/second.
>    Because Bobs's request was issued at time 0 and completed at time 20, Bob 
>    sees a rate of 10 MB/20 seconds = 0.5 MB/second.  If you sum the rates, it
>    looks as though the system is delivering 1.5 MB/second in the interval
>    [0, 10) and 0.5 MB/second in the interval [10, 20).  (You can only 
>    believe the integral of the rates.)
> 

Yes, that's what I do. The important point is that the test took 6 hours
because most of the time no transfer occured and the system just waited.
Otherwise one hour would had been enough. I think the QM only asks two
files at a time and waits for them to be staged before requesting the next
ones.

Luis

--------------------------------------------------------------
Luis M. Bernardo  <lmbernardo@lbl.gov> <www.lbl.gov/~bernardo>  
Scientific Data Management Research & Development Group
Lawrence Berkeley National Laboratory         
Berkeley, CA 94720