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From Michael.Gir...@objectweb.org
Subject Re: java1.4.2 "rws" mode - log write performance - OSX numbers
Date Wed, 15 Sep 2004 17:39:36 GMT
On the survace, test #11 and #15 appear to be very similar, yet there is
a 14x improvement in #15.

Does anyone know enough about the IO to be able to explain why
"rw" write+force is 14x slower than "rwd" write?

Reading the Javadocs, using "rwd" the write blocks until the data is
on disk.  With "rw" the write does not block, but the force(false) 
does block. Since the same amount of data is involved in both cases,
can anyone explain why the "rwd" write is so much faster?

Michael Giroux, ObjectWeb.org


> ------------------------------------------------------------------------ 

> 11. Testing preallocated file using direct buffer + FileChannel "rw" + 
> force(false)
> ------------------------------------------------------------------------ 

>         Chunk size: 4228 bytes
>              Count: 10000
>         Total time: 10226 ms
> Writes per second: 977.899 writes/s
>     Time per chunk: 1.023 ms
>    Write bandwidth: 3.0MB/s
> 
> ------------------------------------------------------------------------ 

> 15. Testing preallocated file using direct buffer + FileChannel "rwd"
> ------------------------------------------------------------------------ 

>         Chunk size: 4228 bytes
>              Count: 10000
>         Total time: 947 ms
> Writes per second: 10559.662 writes/s
>     Time per chunk: 0.095 ms
>    Write bandwidth: 42.0MB/s
> 


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