On Mon, Dec 29, 2003 at 03:03:22PM +0100, Georg Rehfeld wrote:
> Hello Karsten, Gene, all,
> 
Hello Georg,

>
...
> There seem to be no similar figures for taping and the tape speed
> seems to vary largely:
> 
> size  speed    speed
>   MB   MB/s    graph
> 
>  102    1.8    *******
>  108    2.0    ********
>  113    1.7    *******
>  141    2.4    **********
>  227    1.9    ********
>  228    2.1    ********
>  251    1.0    ****
>  253    2.1    ********
>  292    7.0    ****************************
>  294    1.9    ********
>  328    3.2    *************
...
> 
> (All sizes reasonable large, all taping done from holding disk, all
> values from one backup run)
> 
> The ratio of tape speeds is nearly 1:9, a tendency is: larger files
> tape faster, when looking at only sizes > 500 MB the ratio is only
> 1:3.6

Georg,
might you be using HW compression?  If so, might this large
variation in taping speeds actually be greatly influenced
by the compressibility of your data?

I just looked at a report of mine from last evening.  It includes
flushes from several days (forgot to change magazines :(( ) plus
last nights run.  I only see variation from 0.85 - 1.10 MB/s.
Tapetype had reported 1.05 MB/s.

jl
-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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